diff --git a/ast/node.go b/ast/node.go
index fff3a4c..c406908 100644
--- a/ast/node.go
+++ b/ast/node.go
@@ -366,6 +366,15 @@ type Callout struct {
 	ID []byte // number of this callout
 }
 
+// Index is a node that contains an Index item and an optional, subitem.
+type Index struct {
+	Leaf
+
+	Primary bool
+	Item    []byte
+	Subitem []byte
+}
+
 func removeNodeFromArray(a []Node, node Node) []Node {
 	n := len(a)
 	for i := 0; i < n; i++ {
diff --git a/html/renderer.go b/html/renderer.go
index 97d4c92..06654c5 100644
--- a/html/renderer.go
+++ b/html/renderer.go
@@ -869,6 +869,10 @@ func (r *Renderer) callout(w io.Writer, node *ast.Callout) {
 	r.outs(w, "</span>")
 }
 
+func (r *Renderer) index(w io.Writer, node *ast.Index) {
+	// there is no in-text representation.
+}
+
 // RenderNode renders a markdown node to HTML
 func (r *Renderer) RenderNode(w io.Writer, node ast.Node, entering bool) ast.WalkStatus {
 	if r.opts.RenderNodeHook != nil {
@@ -957,6 +961,8 @@ func (r *Renderer) RenderNode(w io.Writer, node ast.Node, entering bool) ast.Wal
 		r.matter(w, node, entering)
 	case *ast.Callout:
 		r.callout(w, node)
+	case *ast.Index:
+		r.index(w, node)
 	default:
 		panic(fmt.Sprintf("Unknown node %T", node))
 	}
diff --git a/parser/ref.go b/parser/ref.go
index 68e2c91..501c1d1 100644
--- a/parser/ref.go
+++ b/parser/ref.go
@@ -1,8 +1,12 @@
 package parser
 
-import "github.com/gomarkdown/markdown/ast"
+import (
+	"bytes"
 
-// parse '(#r)', where r does not contain spaces and is an existing label. Or.
+	"github.com/gomarkdown/markdown/ast"
+)
+
+// parse '(#r)', where r does not contain spaces. Or.
 // (!item) (!item, subitem), for an index, (!!item) signals primary.
 func maybeShortRefOrIndex(p *Parser, data []byte, offset int) (int, ast.Node) {
 	if len(data[offset:]) < 4 {
@@ -11,34 +15,67 @@ func maybeShortRefOrIndex(p *Parser, data []byte, offset int) (int, ast.Node) {
 	// short ref first
 	data = data[offset:]
 	i := 1
-	if data[i] != '#' {
-		return 0, nil
-	}
-	i++
-Loop:
-	for i < len(data) {
-		c := data[i]
-		switch {
-		case c == ')':
-			break Loop
-		case !isAlnum(c):
-			if c == '_' || c == '-' || c == ':' {
-				i++
-				continue
-			}
-			i = 0
-			break Loop
-		}
+	switch data[i] {
+	case '#': // cross ref
 		i++
-	}
-	// end not found or no valid syntax
-	if i == 0 || data[i-1] != ')' {
-		return 0, nil
+	Loop:
+		for i < len(data) {
+			c := data[i]
+			switch {
+			case c == ')':
+				break Loop
+			case !isAlnum(c):
+				if c == '_' || c == '-' || c == ':' {
+					i++
+					continue
+				}
+				i = 0
+				break Loop
+			}
+			i++
+		}
+		// end not found or no valid syntax
+		if i == 0 || data[i-1] != ')' {
+			return 0, nil
+		}
+
+		id := data[2:i]
+		node := &ast.CrossReference{}
+		node.Destination = id
+
+		return i, node
+
+	case '!': // index
+		i++
+		start := i
+		i = skipUntilChar(data, start, ')')
+
+		// did we reach the end of the buffer without a closing marker?
+		if i >= len(data) {
+			return 0, nil
+		}
+
+		if len(data[start:i]) < 1 {
+			return 0, nil
+		}
+		idx := &ast.Index{}
+		idx.Primary = data[start] == '!'
+		buf := data[start:i]
+
+		if idx.Primary {
+			buf = buf[1:]
+		}
+		items := bytes.Split(buf, []byte(","))
+		switch len(items) {
+		case 1:
+			idx.Item = bytes.TrimSpace(items[0])
+			return i + 1, idx
+		case 2:
+			idx.Item = bytes.TrimSpace(items[0])
+			idx.Subitem = bytes.TrimSpace(items[1])
+			return i + 1, idx
+		}
 	}
 
-	id := data[2:i]
-	node := &ast.CrossReference{}
-	node.Destination = id
-
-	return i, node
+	return 0, nil
 }
diff --git a/parser/ref_test.go b/parser/ref_test.go
index 0177fb3..4738f1c 100644
--- a/parser/ref_test.go
+++ b/parser/ref_test.go
@@ -36,3 +36,58 @@ func TestCrossReference(t *testing.T) {
 		}
 	}
 }
+
+func TestIndex(t *testing.T) {
+	p := New()
+
+	tests := []struct {
+		data []byte
+		i    *ast.Index
+		fail bool
+	}{
+		// ok
+		{
+			data: []byte("(!yes)"),
+			i:    &ast.Index{Item: []byte("yes")},
+		},
+		{
+			data: []byte("(!y:es)"),
+			i:    &ast.Index{Item: []byte("y:es")},
+		},
+		{
+			data: []byte("(!yes, no)"),
+			i:    &ast.Index{Item: []byte("yes"), Subitem: []byte("no")},
+		},
+		{
+			data: []byte("(!  yes  , no  )"),
+			i:    &ast.Index{Item: []byte("yes"), Subitem: []byte("no")},
+		},
+		// fails
+		{data: []byte("(!yes"), fail: true},
+		{data: []byte("(_yes"), fail: true},
+	}
+
+	for i, test := range tests {
+		_, n := maybeShortRefOrIndex(p, test.data, 0)
+		if test.fail && n != nil {
+			t.Errorf("test %d, should have failed to parse %s", i, test.data)
+			continue
+		}
+		if test.fail && n == nil {
+			// ok
+			continue
+		}
+
+		idx := n.(*ast.Index)
+
+		if string(test.i.Item) != string(idx.Item) {
+			t.Errorf("test %d, got item %s, wanted %s", i, idx.Item, test.i.Item)
+		}
+		if string(test.i.Subitem) != string(idx.Subitem) {
+			t.Errorf("test %d, got item %s, wanted %s", i, idx.Subitem, test.i.Subitem)
+		}
+		if test.i.Primary != idx.Primary {
+			t.Errorf("test %d, got item %t, wanted %t", i, idx.Primary, test.i.Primary)
+		}
+	}
+}
diff --git a/testdata/mmark.test b/testdata/mmark.test
index ff6b6bc..59bbe7c 100644
--- a/testdata/mmark.test
+++ b/testdata/mmark.test
@@ -79,3 +79,14 @@ code
 ---
 <pre><code class="myclass1 myclass2">code
 </code></pre>
+---
+# Index
+(!myitem, subitem)
+(!!item)
+(!!item,   subtitem  )
+---
+<h1>Index</h1>
+
+<p>
+
+</p>