A series of substituted (±) 3, 5-diphenyl-2-thioxoimidazolin-4-ones was synthesized in order to design new type-2 cyclooxygenase (COX-2) inhibitors. This study has led to molecules which completely inhibit human recombinant COX-2 at 50μM. Molecular modelling highlighted drug interactions with the active site of both cyclooxygenases and suggested modifications to enhance the selectivity of the compounds. In human blood, COX-2 ...