When using the SharePoint webservice lists.asmx you can create a simple CAML query to retrieve listitems. I discovered that when no RowLimit is set the result does not return more than 100 items. So if you want to retrieve more than 100 items be sure to specify the RowLimit when calling GetListItems.
The example below is in Delphi code:
The code above will return all items using a max limit of 5000 items. The code below will only return 100 items regardless of the “real” amount of list items specified.