diff --git a/src/gn/command_format.cc b/src/gn/command_format.cc
index 668fedd..3cc4218 100644
--- a/src/gn/command_format.cc
+++ b/src/gn/command_format.cc
@@ -135,6 +135,10 @@
 
   void TrimAndPrintToken(const Token& token);
 
+  void PrintTrailingCommentsWrapped(const std::vector<Token>& comments);
+
+  void PrintSuffixComments(const ParseNode* node);
+
   // End the current line, flushing end of line comments.
   void Newline();
 
@@ -276,23 +280,74 @@
   Print(trimmed);
 }
 
+// Assumes that the margin is set to the indent level where the comments should
+// be aligned. This doesn't de-wrap, it only wraps. So if a suffix comment
+// causes the line to exceed 80 col it will be wrapped, but the subsequent line
+// would fit on the then-broken line it will not be merged with it. This is
+// partly because it's difficult to implement at this level, but also because
+// it can break hand-authored line breaks where they're starting a new paragraph
+// or statement.
+void Printer::PrintTrailingCommentsWrapped(const std::vector<Token>& comments) {
+  bool have_empty_line = true;
+  auto start_next_line = [this, &have_empty_line]() {
+    Trim();
+    Print("\n");
+    PrintMargin();
+    have_empty_line = true;
+  };
+  for (const auto& c : comments) {
+    if (!have_empty_line) {
+      start_next_line();
+    }
+
+    std::string trimmed;
+    TrimWhitespaceASCII(std::string(c.value()), base::TRIM_ALL, &trimmed);
+
+    if (margin() + trimmed.size() <= kMaximumWidth) {
+      Print(trimmed);
+      have_empty_line = false;
+    } else {
+      bool continuation = false;
+      std::vector<std::string> split_on_spaces = base::SplitString(
+          c.value(), " ", base::WhitespaceHandling::TRIM_WHITESPACE,
+          base::SplitResult::SPLIT_WANT_NONEMPTY);
+      for (size_t j = 0; j < split_on_spaces.size(); ++j) {
+        if (have_empty_line && continuation) {
+          Print("# ");
+        }
+        Print(split_on_spaces[j]) ;
+        Print(" ");
+        if (split_on_spaces[j] != "#") {
+          have_empty_line = false;
+        }
+        if (!have_empty_line &&
+            (j < split_on_spaces.size() - 1 &&
+             CurrentColumn() + split_on_spaces[j + 1].size() > kMaximumWidth)) {
+          start_next_line();
+          continuation = true;
+        }
+      }
+    }
+  }
+}
+
+// Used during penalty evaluation, similar to Newline().
+void Printer::PrintSuffixComments(const ParseNode* node) {
+  if (node->comments() && !node->comments()->suffix().empty()) {
+    Print("  ");
+    stack_.push_back(IndentState(CurrentColumn(), false, false));
+    PrintTrailingCommentsWrapped(node->comments()->suffix());
+    stack_.pop_back();
+  }
+}
+
 void Printer::Newline() {
   if (!comments_.empty()) {
     Print("  ");
     // Save the margin, and temporarily set it to where the first comment
-    // starts so that multiple suffix comments are vertically aligned. This
-    // will need to be fancier once we enforce 80 col.
+    // starts so that multiple suffix comments are vertically aligned.
     stack_.push_back(IndentState(CurrentColumn(), false, false));
-    int i = 0;
-    for (const auto& c : comments_) {
-      if (i > 0) {
-        Trim();
-        Print("\n");
-        PrintMargin();
-      }
-      TrimAndPrintToken(c);
-      ++i;
-    }
+    PrintTrailingCommentsWrapped(comments_);
     stack_.pop_back();
     comments_.clear();
   }
@@ -519,8 +574,11 @@
 bool Printer::ExceedsMaximumWidth(const std::string& output) {
   for (const auto& line : base::SplitString(output, "\n", base::KEEP_WHITESPACE,
                                             base::SPLIT_WANT_ALL)) {
-    if (line.size() > kMaximumWidth)
+    std::string_view trimmed =
+        TrimString(line, " ", base::TrimPositions::TRIM_TRAILING);
+    if (trimmed.size() > kMaximumWidth) {
       return true;
+    }
   }
   return false;
 }
@@ -639,6 +697,8 @@
     int penalty_current_line =
         sub1.Expr(binop->right(), prec_right, std::string());
     sub1.Print(suffix);
+    sub1.PrintSuffixComments(root);
+    sub1.PrintSuffixComments(binop->right());
     penalty_current_line += AssessPenalty(sub1.String());
     if (!is_assignment && left_is_multiline) {
       // In e.g. xxx + yyy, if xxx is already multiline, then we want a penalty
@@ -654,6 +714,8 @@
     int penalty_next_line =
         sub2.Expr(binop->right(), prec_right, std::string());
     sub2.Print(suffix);
+    sub2.PrintSuffixComments(root);
+    sub2.PrintSuffixComments(binop->right());
     penalty_next_line += AssessPenalty(sub2.String());
 
     // Force a list on the RHS that would normally be a single line into
@@ -669,6 +731,8 @@
       sub3.stack_.push_back(IndentState(start_column, false, false));
       sub3.Sequence(kSequenceStyleList, rhs_list->contents(), rhs_list->End(),
                     true);
+      sub3.PrintSuffixComments(root);
+      sub3.PrintSuffixComments(binop->right());
       sub3.stack_.pop_back();
       penalty_multiline_rhs_list = AssessPenalty(sub3.String());
       tried_rhs_multiline = true;
@@ -1026,10 +1090,13 @@
   if (end && end->comments() && !end->comments()->before().empty())
     return true;
 
-  // If there's before line comments, make sure we have a place to put them.
+  // If there's before or suffix line comments, make sure we have a place to put
+  // them.
   for (const auto& i : list) {
-    if (i->comments() && !i->comments()->before().empty())
+    if (i->comments() && (!i->comments()->before().empty() ||
+                          !i->comments()->suffix().empty())) {
       return true;
+    }
   }
 
   // When a scope is used as a list entry, it's too complicated to go one a
diff --git a/src/gn/command_format_unittest.cc b/src/gn/command_format_unittest.cc
index f334b70..503e6cf 100644
--- a/src/gn/command_format_unittest.cc
+++ b/src/gn/command_format_unittest.cc
@@ -83,11 +83,11 @@
 FORMAT_TEST(037)
 FORMAT_TEST(038)
 FORMAT_TEST(039)
-// TODO(scottmg): Bad break, exceeding 80 col: FORMAT_TEST(040)
+FORMAT_TEST(040)
 FORMAT_TEST(041)
 FORMAT_TEST(042)
 FORMAT_TEST(043)
-// TODO(scottmg): Dewrapped caused exceeding 80 col: FORMAT_TEST(044)
+FORMAT_TEST(044)
 FORMAT_TEST(045)
 FORMAT_TEST(046)
 FORMAT_TEST(047)
@@ -121,3 +121,6 @@
 FORMAT_TEST(074)
 FORMAT_TEST(075)
 FORMAT_TEST(076)
+FORMAT_TEST(077)
+FORMAT_TEST(078)
+FORMAT_TEST(079)
diff --git a/src/gn/format_test_data/040.gn b/src/gn/format_test_data/040.gn
index 1f4754e..63e5b07 100644
--- a/src/gn/format_test_data/040.gn
+++ b/src/gn/format_test_data/040.gn
@@ -1,4 +1,4 @@
-# Dewrapping shouldn't cause 80 col to be exceed.
+# Dewrapping shouldn't cause 80 col to be exceeded.
 # 80 ---------------------------------------------------------------------------
 if (true) {
   if (is_win) {
diff --git a/src/gn/format_test_data/040.golden b/src/gn/format_test_data/040.golden
new file mode 100644
index 0000000..89fdacf
--- /dev/null
+++ b/src/gn/format_test_data/040.golden
@@ -0,0 +1,10 @@
+# Dewrapping shouldn't cause 80 col to be exceeded.
+# 80 ---------------------------------------------------------------------------
+if (true) {
+  if (is_win) {
+    cflags = [
+      "/wd4267",  # TODO(jschuh): crbug.com/167187 fix size_t to int
+                  # truncations.
+    ]
+  }
+}
diff --git a/src/gn/format_test_data/044.gn b/src/gn/format_test_data/044.gn
index fe09617..030c5dd 100644
--- a/src/gn/format_test_data/044.gn
+++ b/src/gn/format_test_data/044.gn
@@ -1,3 +1,4 @@
+# 80 ---------------------------------------------------------------------------
 config("compiler") {
   if (is_win) {
     if (is_component_build) {
diff --git a/src/gn/format_test_data/077.gn b/src/gn/format_test_data/077.gn
new file mode 100644
index 0000000..665d420
--- /dev/null
+++ b/src/gn/format_test_data/077.gn
@@ -0,0 +1,6 @@
+# Regression test for https://crbug.com/gn/138. 80 col -------------------------
+foo("bar") {
+  blah = [
+    "$target_gen_dir/run-lit",  # Non-existing, so that ninja runs it each time.
+  ]
+}
diff --git a/src/gn/format_test_data/077.golden b/src/gn/format_test_data/077.golden
new file mode 100644
index 0000000..665d420
--- /dev/null
+++ b/src/gn/format_test_data/077.golden
@@ -0,0 +1,6 @@
+# Regression test for https://crbug.com/gn/138. 80 col -------------------------
+foo("bar") {
+  blah = [
+    "$target_gen_dir/run-lit",  # Non-existing, so that ninja runs it each time.
+  ]
+}
diff --git a/src/gn/format_test_data/078.gn b/src/gn/format_test_data/078.gn
new file mode 100644
index 0000000..9b1369a
--- /dev/null
+++ b/src/gn/format_test_data/078.gn
@@ -0,0 +1,15 @@
+# 80 ---------------------------------------------------------------------------
+# Long suffix comments, and including trailing spaces.
+config("compiler") {
+  if (is_win) {
+    if (is_component_build) {
+      cflags += [
+        "/EHsc",  # These are some very long suffix comment words aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
+                  # bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb   
+                  # cccccccccccccccccccccccccccccccccccccccccccccccccccccccccccc
+                  # dddddddddddddddd ddddddddddd dddddddd ddddddddddddd ddddddddddddddd
+      ]
+    }
+  }
+}
+
diff --git a/src/gn/format_test_data/078.golden b/src/gn/format_test_data/078.golden
new file mode 100644
index 0000000..ea96580
--- /dev/null
+++ b/src/gn/format_test_data/078.golden
@@ -0,0 +1,16 @@
+# 80 ---------------------------------------------------------------------------
+# Long suffix comments, and including trailing spaces.
+config("compiler") {
+  if (is_win) {
+    if (is_component_build) {
+      cflags += [
+        "/EHsc",  # These are some very long suffix comment words
+                  # aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
+                  # bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb
+                  # cccccccccccccccccccccccccccccccccccccccccccccccccccccccccccc
+                  # dddddddddddddddd ddddddddddd dddddddd ddddddddddddd
+                  # ddddddddddddddd
+      ]
+    }
+  }
+}
diff --git a/src/gn/format_test_data/079.gn b/src/gn/format_test_data/079.gn
new file mode 100644
index 0000000..9218757
--- /dev/null
+++ b/src/gn/format_test_data/079.gn
@@ -0,0 +1,14 @@
+# 80 ---------------------------------------------------------------------------
+# Somewhat more intelligent suffix comments.
+
+core_generated_interface_idl_files = generated_webcore_testing_idl_files  # interfaces
+
+core_generated_interface_idl_files = generated_webcore_testing_idl_files_and_some_more_longer # stuff
+
+if (true) {
+  if (true) {
+    if (true) {
+      dllname = "{{output_dir}}/{{target_output_name}}{{output_extension}}"  # e.g. foo.dll
+    }
+  }
+}
diff --git a/src/gn/format_test_data/079.golden b/src/gn/format_test_data/079.golden
new file mode 100644
index 0000000..c4617b5
--- /dev/null
+++ b/src/gn/format_test_data/079.golden
@@ -0,0 +1,18 @@
+# 80 ---------------------------------------------------------------------------
+# Somewhat more intelligent suffix comments.
+
+core_generated_interface_idl_files =
+    generated_webcore_testing_idl_files  # interfaces
+
+core_generated_interface_idl_files =
+    generated_webcore_testing_idl_files_and_some_more_longer  # stuff
+
+if (true) {
+  if (true) {
+    if (true) {
+      dllname =
+          "{{output_dir}}/{{target_output_name}}{{output_extension}}"  # e.g.
+                                                                       # foo.dll
+    }
+  }
+}