Fruits of Coriandrum sativum Linn have been described in Unani literature to possess anti-gastritis, anti-ulcer, sedative, hypnotic, anti-anxiety and anti-stress activity. It has been studied scientifically for anti-ulcer activity on some of the parameters but no study has been conducted so far, for its role in aspirin induced gastric ulcer. The present study was designed to investigate the anti ulcer activity of hydro alcoholic extract of coriander against aspirin induced gastric ulcer in Wistar rats of either sex, weighing 150-200 gm. The animals were divided into 8 groups of 8 animals each. Different groups represented plain control (vehicle), negative control (ulcer induced), standard control (pre and post-treated with ranitidine) and four test groups, two each for preventive (pre-treated with 160 mg/kg and 273 mg/kg of extract) and curative (post-treated with 160 mg/kg and 273 mg/ kg of extract) studies. Animals were treated for five days before or after the ulcer induction and sacrificed thereafter. Their stomach was dissected out and observed for lesions. The scoring of lesions was done to calculate the ulcer index and ulcer score. Histopathological studies were also carried out.