diff --git a/data/test/ignore b/data/test/ignore
index af3dd507..60dd1e87 100644
--- a/data/test/ignore
+++ b/data/test/ignore
@@ -1,6 +1,3 @@
-tb: isindex.dat-0
-tb: isindex.dat-1
-tb: isindex.dat-2
 tb: ruby.dat-0
 tb: ruby.dat-1
 tb: ruby.dat-10
@@ -13,14 +10,8 @@ tb: ruby.dat-20
 tb: ruby.dat-3
 tb: ruby.dat-5
 tb: ruby.dat-7
-tb: tests19.dat-10
-tb: tests19.dat-11
 tb: tests19.dat-18
 tb: tests19.dat-21
-tb: tests19.dat-7
-tb: tests19.dat-8
-tb: tests19.dat-9
-tb: tests2.dat-44
 tb: tests20.dat-34
 tb: tests20.dat-35
 tb: tests20.dat-36
diff --git a/src/tree_builder/rules.expanded.rs b/src/tree_builder/rules.expanded.rs
index 7495b88f..492281bd 100644
--- a/src/tree_builder/rules.expanded.rs
+++ b/src/tree_builder/rules.expanded.rs
@@ -8,15 +8,15 @@
 // except according to those terms.
 
 // This file is generated from rules.rs
-// source SipHash: 4083772598771558827
+// source SipHash: 6604065678599019684
 
 # ! [
 doc =
     "//! The tree builder rules, as a single, enormous nested match expression."
 ] use tree_builder::types::*; use tree_builder::tag_sets::*;
-use tree_builder::actions::TreeBuilderActions;
+use tree_builder::actions::{NoPush, Push, TreeBuilderActions};
 use tree_builder::interface::{TreeSink, Quirks, AppendNode, NextParserState};
-use tokenizer::{Tag, StartTag, EndTag};
+use tokenizer::{Attribute, EndTag, StartTag, Tag};
 use tokenizer::states::{Rcdata, Rawtext, ScriptData, Plaintext, Quiescent};
 use util::str::is_ascii_whitespace; use std::ascii::AsciiExt;
 use std::mem::replace; use std::borrow::Cow::Borrowed;
@@ -1169,10 +1169,52 @@ impl <Handle, Sink> TreeBuilderStep for super::TreeBuilder<Handle, Sink> where
                     self.unexpected(&tag);
                     self.step(InBody, TagToken(Tag{name: atom!(img), ..tag}))
                 }
-                ::tree_builder::types::TagToken(::tokenizer::Tag {
+                ::tree_builder::types::TagToken(tag@::tokenizer::Tag {
                                                 kind: ::tokenizer::StartTag,
                                                 name: atom!(isindex), .. }) =>
-                panic!("FIXME: <isindex> not implemented"),
+                {
+                    self.unexpected(&tag);
+                    let in_template =
+                        self.in_html_elem_named(atom!(template));
+                    if !in_template && self.form_elem.is_some() {
+                        return Done;
+                    }
+                    self.frameset_ok = false;
+                    self.close_p_element_in_button_scope();
+                    let mut form_attrs = vec!();
+                    let mut prompt = None;
+                    let mut input_attrs = vec!();
+                    for attr in tag.attrs.into_iter() {
+                        match attr.name {
+                            qualname!("" , action) => form_attrs.push(attr),
+                            qualname!("" , prompt) =>
+                            prompt = Some(attr.value),
+                            qualname!("" , name) => { }
+                            _ => input_attrs.push(attr),
+                        }
+                    }
+                    input_attrs.push(Attribute{name: qualname!("" , name),
+                                               value:
+                                                   "isindex".to_tendril(),});
+                    let form =
+                        self.insert_element(Push, ns!(HTML), atom!(form),
+                                            form_attrs);
+                    if !in_template { self.form_elem = Some(form.clone()); }
+                    self.insert_element(NoPush, ns!(HTML), atom!(hr), vec!());
+                    self.reconstruct_formatting();
+                    self.insert_element(Push, ns!(HTML), atom!(label),
+                                        vec!());
+                    self.append_text(prompt.unwrap_or_else(|| {
+                                                           "This is a searchable index. Enter search keywords: ".to_tendril()
+                                                       }));
+                    self.insert_element(NoPush, ns!(HTML), atom!(input),
+                                        input_attrs);
+                    self.pop();
+                    self.insert_element(NoPush, ns!(HTML), atom!(hr), vec!());
+                    self.pop();
+                    if !in_template { self.form_elem = None; }
+                    DoneAckSelfClosing
+                }
                 ::tree_builder::types::TagToken(tag@::tokenizer::Tag {
                                                 kind: ::tokenizer::StartTag,
                                                 name: atom!(textarea), .. })
diff --git a/src/tree_builder/rules.rs b/src/tree_builder/rules.rs
index 8ed47c86..e2a03558 100644
--- a/src/tree_builder/rules.rs
+++ b/src/tree_builder/rules.rs
@@ -11,10 +11,10 @@
 
 use tree_builder::types::*;
 use tree_builder::tag_sets::*;
-use tree_builder::actions::TreeBuilderActions;
+use tree_builder::actions::{NoPush, Push, TreeBuilderActions};
 use tree_builder::interface::{TreeSink, Quirks, AppendNode, NextParserState};
 
-use tokenizer::{Tag, StartTag, EndTag};
+use tokenizer::{Attribute, EndTag, StartTag, Tag};
 use tokenizer::states::{Rcdata, Rawtext, ScriptData, Plaintext, Quiescent};
 
 use util::str::is_ascii_whitespace;
@@ -629,7 +629,48 @@ impl<Handle, Sink> TreeBuilderStep
                     }))
                 }
 
-                <isindex> => panic!("FIXME: <isindex> not implemented"),
+                tag @ <isindex> => {
+                    self.unexpected(&tag);
+                    let in_template = self.in_html_elem_named(atom!(template));
+                    if !in_template && self.form_elem.is_some() {
+                        return Done;
+                    }
+                    self.frameset_ok = false;
+                    self.close_p_element_in_button_scope();
+                    let mut form_attrs = vec![];
+                    let mut prompt = None;
+                    let mut input_attrs = vec![];
+                    for attr in tag.attrs.into_iter() {
+                        match attr.name {
+                            qualname!("", action) => form_attrs.push(attr),
+                            qualname!("", prompt) => prompt = Some(attr.value),
+                            qualname!("", name) => {},
+                            _ => input_attrs.push(attr),
+                        }
+                    }
+                    input_attrs.push(Attribute {
+                        name: qualname!("", name),
+                        value: "isindex".to_tendril(),
+                    });
+                    let form = self.insert_element(Push, ns!(HTML), atom!(form), form_attrs);
+                    if !in_template {
+                        self.form_elem = Some(form.clone());
+                    }
+                    self.insert_element(NoPush, ns!(HTML), atom!(hr), vec![]);
+                    self.reconstruct_formatting();
+                    self.insert_element(Push, ns!(HTML), atom!(label), vec![]);
+                    self.append_text(prompt.unwrap_or_else(|| {
+                        "This is a searchable index. Enter search keywords: ".to_tendril()
+                    }));
+                    self.insert_element(NoPush, ns!(HTML), atom!(input), input_attrs);
+                    self.pop();
+                    self.insert_element(NoPush, ns!(HTML), atom!(hr), vec![]);
+                    self.pop();
+                    if !in_template {
+                        self.form_elem = None;
+                    }
+                    DoneAckSelfClosing
+                }
 
                 tag @ <textarea> => {
                     self.ignore_lf = true;