Mucked around for a few hours and made the changes you suggested above. Still got unfiltered - all results for all products when I click a dropdown product category at http://outofchaos.net/gsc/www/menu2.php The Category_ID field is in both the Category and Products tables of the DB and the generated URL looks right, eg http://outofchaos.net/gsc/www/products_results.php?Category_ID=6 but should show only the one product="Artic White' but shows all. Could there be some reference to Category_ID in products_results.php that I am missing? Any other suggestions? Thanks again for your help.