diff --git a/lib/jekyll/migrators/tumblr.rb b/lib/jekyll/migrators/tumblr.rb
index 10f41601..0f9c227c 100644
--- a/lib/jekyll/migrators/tumblr.rb
+++ b/lib/jekyll/migrators/tumblr.rb
@@ -3,93 +3,179 @@ require 'open-uri'
 require 'fileutils'
 require 'date'
 require 'json'
+require 'uri'
+require 'jekyll'
 
 module Jekyll
   module Tumblr
-    def self.process(url, grab_images = false, format = "html")
-      current_page = 0
-
-      while true
-
-        f = open(url + "/api/read/json/?num=50&start=#{current_page * 50}")
-        # [21...-2] strips Tumblr's Javascript/JSONP start/end chars
-        json = f.readlines.join("\n")[21...-2]
+    def self.process(url, format = "html", grab_images = false,
+                     add_highlights = false, rewrite_urls = true)
+      FileUtils.mkdir_p "_posts/tumblr"
+      url += "/api/read/json/"
+      per_page = 50
+      posts = []
+      # Two passes are required so that we can rewrite URLs.
+      # First pass builds up an array of each post as a hash.
+      begin
+        current_page = (current_page || -1) + 1
+        feed = open(url + "?num=#{per_page}&start=#{current_page * per_page}")
+        json = feed.readlines.join("\n")[21...-2]  # Strip Tumblr's JSONP chars.
         blog = JSON.parse(json)
         puts "Page: #{current_page + 1} - Posts: #{blog["posts"].size}"
-        FileUtils.mkdir_p "_posts/tumblr"
-
-        blog["posts"].each do |post|
-
-          case post['type']
-            when "regular"
-              title = post["regular-title"]
-              content = post["regular-body"]
-            when "link"
-              title = post["link-text"] || post["link-url"]
-              content = "<a href=\"#{post["link-url"]}\">#{title}</a>"
-              content << "<br/>" + post["link-description"] unless post["link-description"].nil?
-            when "photo"
-              title = post["photo-caption"]
-              content = "<img src=\"#{save_file(post["photo-url"], grab_images)}\"/>"
-              content = "<a href=\"#{post["photo-link-url"]}\">#{content}</a>" unless post["photo-link-url"].nil?
-            when "audio"
-              if !post["id3-title"].nil?
-                title = post["id3-title"]
-                content = post.at["audio-player"] + "<br/>" + post["audio-caption"]
-              else
-                title = post["audio-caption"]
-                content = post.at["audio-player"]
-              end
-            when "quote"
-              title = post["quote-text"]
-              content = "<blockquote>#{post["quote-text"]}</blockquote>"
-              content << "&#8212;" + post["quote-source"] unless post["quote-source"].nil?
-            when "conversation"
-              title = post["conversation-title"]
-              content = "<section><dialog>"
-              post["conversation"]["line"].each do |line|
-                content << "<dt>#{line['label']}</dt><dd>#{line}</dd>"
-              end
-              content << "</section></dialog>"
-            when "video"
-              title = post["video-title"]
-              content = post["video-player"]
-              content << "<br/>" + post["video-caption"] unless post["video-caption"].nil?
-          end # End post types
-
-          name = "#{Date.parse(post['date']).to_s}-#{title.downcase.strip.gsub(' ', '-').gsub(/[^\w-]/, '')}.#{format}"
-
-          File.open("_posts/tumblr/#{name}", "w") do |f|
-            if format == "md"
-                preserve = ["table", "tr", "th", "td"]
-                preserve.each { |tag| content = content.gsub(/<#{tag}/i, "$$" + tag).gsub(/<\/#{tag}/i, "||" + tag) }
-                content = %x[echo '#{content.gsub("'", "''")}' | html2text]
-                preserve.each { |tag| content = content.gsub("$$" + tag, "<" + tag).gsub("||" + tag, "</" + tag) }
-            end
-            header = {"layout" => "post", "title" => title, "tags" => post["tags"]}
-            f.puts header.to_yaml + "---\n" + content
-          end # End file
-
-        end # End post XML
-
-        if blog["posts"].size < 50
-          break
+        posts += blog["posts"].map { |post| post_to_hash(post, format) }
+      end until blog["posts"].size < per_page
+      # Rewrite URLs and create redirects.
+      posts = rewrite_urls_and_redirects posts if rewrite_urls
+      # Second pass for writing post files.
+      posts.each do |post|
+        if format == "md"
+          post[:content] = html_to_markdown post[:content]
+          post[:content] = add_syntax_highlights post[:content] if add_highlights
         end
-        current_page += 1
-
-      end # End while loop
-    end # End method
+        File.open("_posts/tumblr/#{post[:name]}", "w") do |f|
+          f.puts post[:header].to_yaml + "---\n" + post[:content]
+        end
+      end
+    end
 
     private
 
+    # Converts each type of Tumblr post to a hash with all required
+    # data for Jekyll.
+    def self.post_to_hash(post, format)
+      case post['type']
+        when "regular"
+          title = post["regular-title"]
+          content = post["regular-body"]
+        when "link"
+          title = post["link-text"] || post["link-url"]
+          content = "<a href=\"#{post["link-url"]}\">#{title}</a>"
+          unless post["link-description"].nil?
+            content << "<br/>" + post["link-description"]
+          end
+        when "photo"
+          title = post["photo-caption"]
+          content = "<img src=\"#{save_file(post["photo-url"], grab_images)}\"/>"
+          unless post["photo-link-url"].nil?
+            content = "<a href=\"#{post["photo-link-url"]}\">#{content}</a>"
+          end
+        when "audio"
+          if !post["id3-title"].nil?
+            title = post["id3-title"]
+            content = post.at["audio-player"] + "<br/>" + post["audio-caption"]
+          else
+            title = post["audio-caption"]
+            content = post.at["audio-player"]
+          end
+        when "quote"
+          title = post["quote-text"]
+          content = "<blockquote>#{post["quote-text"]}</blockquote>"
+          unless post["quote-source"].nil?
+            content << "&#8212;" + post["quote-source"]
+          end
+        when "conversation"
+          title = post["conversation-title"]
+          content = "<section><dialog>"
+          post["conversation"]["line"].each do |line|
+            content << "<dt>#{line['label']}</dt><dd>#{line}</dd>"
+          end
+          content << "</section></dialog>"
+        when "video"
+          title = post["video-title"]
+          content = post["video-player"]
+          unless post["video-caption"].nil?
+            content << "<br/>" + post["video-caption"]
+          end
+      end
+      date = Date.parse(post['date']).to_s
+      slug = title.downcase.strip.gsub(' ', '-').gsub(/[^\w-]/, '')
+      {
+        :name => "#{date}-#{slug}.#{format}",
+        :header => {
+          "layout" => "post",
+          "title" => title,
+          "tags" => post["tags"],
+        },
+        :content => content,
+        :url => post["url"],
+        :slug => post["url-with-slug"],
+      }
+    end
+
+    # Create a Hash of old urls => new urls, for rewriting and
+    # redirects, and replace urls in each post. Instantiate Jekyll
+    # site/posts to get the correct permalink format.
+    def self.rewrite_urls_and_redirects(posts)
+      site = Jekyll::Site.new(Jekyll.configuration({}))
+      dir = File.join(File.dirname(__FILE__), "..")
+      urls = Hash[posts.map { |post|
+        tumblr_url = URI.parse(post[:slug]).path
+        jekyll_url = Jekyll::Post.new(site, dir, "", "tumblr/" + post[:name]).url
+        redirect_dir = tumblr_url.sub(/\//, "") + "/"
+        FileUtils.mkdir_p redirect_dir
+        File.open(redirect_dir + "index.html", "w") do |f|
+          f.puts "<html><head><meta http-equiv='Refresh' content='0; " +
+                 "url=#{jekyll_url}'></head><body></body></html>"
+        end
+        [tumblr_url, jekyll_url]
+      }]
+      posts.map { |post|
+        urls.each do |tumblr_url, jekyll_url|
+          post[:content].gsub!(/#{tumblr_url}/i, jekyll_url)
+        end
+        post
+      }
+    end
+
+    # Uses Python's html2text to convert a post's content to
+    # markdown. Preserve HTML tables as per the markdown docs.
+    def self.html_to_markdown(content)
+      preserve = ["table", "tr", "th", "td"]
+      preserve.each do |tag|
+        content.gsub!(/<#{tag}/i, "$$" + tag)
+        content.gsub!(/<\/#{tag}/i, "||" + tag)
+      end
+      content = %x[echo '#{content.gsub("'", "''")}' | html2text]
+      preserve.each do |tag|
+        content.gsub!("$$" + tag, "<" + tag)
+        content.gsub!("||" + tag, "</" + tag)
+      end
+      content
+    end
+
+    # Adds pygments highlight tags to code blocks in posts that use
+    # markdown format. This doesn't guess the language of the code
+    # block, so you should modify this to suit your own content.
+    # For example, my code block only contain Python and JavaScript,
+    # so I can assume the block is JavaScript if it contains a
+    # semi-colon.
+    def self.add_syntax_highlights(content)
+      lines = content.split("\n")
+      block, indent, lang, start = false, /^    /, nil, nil
+      lines.each_with_index do |line, i|
+        if !block && line =~ indent
+          block = true
+          lang = "python"
+          start = i
+        elsif block
+          lang = "javascript" if line =~ /;$/
+          block = line =~ indent && i < lines.size - 1 # Also handle EOF
+          if !block
+            lines[start] = "{% highlight #{lang} %}"
+            lines[i - 1] = "{% endhighlight %}"
+          end
+          lines[i] = lines[i].sub(indent, "")
+        end
+      end
+      lines.join("\n")
+    end
+
     def self.save_file(url, grab_image = false)
       unless grab_image == false
         FileUtils.mkdir_p "tumblr_files"
-
         File.open("tumblr_files/#{url.split('/').last}", "w") do |f|
           f.write(open(url).read)
         end
-
         return "/tumblr_files/#{url.split('/').last}"
       else
         return url