In this study, the effects of nimesulide on the antiinflammatory and ulcerative action of some nonsteroidal antiinflammatory drugs (NSAIDs; (diclofenac sodium, ibuprofen, meloxicam) were investigated in rats, and it was determined whether nimesulide interacts with these drugs in vivo and in vitro. Results showed that while diclofenac sodium, ibuprofen, and meloxicam reduced carrageenan-induced paw edema in rats by 66%, 39.6%, and 58%, respectively, when used alone, they reduced carrageenan-induced paw edema by 69.8%, 56.6%, and 66%, respectively, when combined with nimesulide. Diclofenac (25 mg kg(-1)) and meloxicam (7.5 mg kg(-1)) produced 9.3 and 19.6 mm(2) ulcer areas in stomachs of rats, respectively, when used alone, but when combined with nimesulide diclofenac and meloxicam did not cause any injury in rat stomachs. While ranitidine at 100 mg kg(-1) dose prevented diclofenac-induced ulcer formation, it reduced meloxicam-induced ulcer formation significantly. We conclude that nimesulide does not interact with these drugs in terms of antiinflammatory action and antagonizes their side effects on gastric tissue without reacting chemically.