The one-based index of the first item in the results feed.
This should <emphasis>not</emphasis> be used manually for pagination. Instead, use a Query and call its next_page or previous_page functions before making the query to the service.
API reference: <ulink type="http" url="http://code.google.com/apis/youtube/2.0/reference.html#youtube_data_api_tag_openSearch:startIndex"> openSearch:startIndex< /ulink>