diff --git a/html/syntax/serializing-html-fragments/processing-instructions.html b/html/syntax/serializing-html-fragments/processing-instructions.html
new file mode 100644
index 00000000000000..7cb1bd7083e73d
--- /dev/null
+++ b/html/syntax/serializing-html-fragments/processing-instructions.html
@@ -0,0 +1,21 @@
+<!DOCTYPE html>
+<title>ProcessingInstruction serialization in HTML</title>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script>
+test(function() {
+  const pi = document.createProcessingInstruction("target", "data");
+  const div = document.createElement("div");
+  div.appendChild(pi);
+  assert_equals(div.innerHTML, "<?target data>");
+}, "PI created by document.createProcessingInstruction()");
+
+test(function() {
+  const parser = new DOMParser();
+  const xmlDoc = parser.parseFromString("<root><?target data?></root>", "text/xml");
+  const pi = xmlDoc.documentElement.firstChild;
+  const div = document.createElement("div");
+  div.appendChild(pi);
+  assert_equals(div.innerHTML, "<?target data>");
+}, "PI adopted from XML document");
+</script>
