Aim: Acetylsalicylic acid (ASA, aspirin), which is one of the most frequently used drugs in the world. causes severe gastric mucosal injury. Nitric oxide (NO) is synthesized from L-arginine by nitric oxide synthase (NOS). NOS can be inhibited by N omega-nitro-L-arginine methyl ester (L-NAME) and stimulated by supplementing the diet with L-arginine (L-Arg). The aim of this study was to investigate the role of NO on gastric mucosal injury induced by ASA.