In the present study free radical scavenging and antiulcer potential of Benincasa hispida seeds was evaluated. The powdered seeds were extracted with methanol. The extract was evaluated for its free radical scavenging activity by DPPH method followed by antiulcer activity using pyloric ligation, water immersion stress and NSAID (indomethacin) induced gastric ulcer model (NIU) in rats. The parameters assessed were gastric volume, free acidity, total acidity, ulcer index and percentage ulcer protection. Ranitidine was used as the reference antiulcer drug. The methanolic extract showed concentration dependent DPPH radical scavenging activity. The methanolic extract of Benincasa hispida seeds (MEBH) inhibited gastric ulceration by decreasing the gastric volume, free and total acidity. The high dose (300 mg kg-1) showed significant reduction in the above parameters which was comparable to the standard drug ranitidine (p<0.05). The MEBH caused 52.7, 67.4 and 61.2% inhibition of ulcers in pyloric ligation, water immersion stress and NSAID induced ulcer models, respectively at 300 mg kg-1. Thus it can be concluded that the seeds of Benincasa hispida possess potent antiulcer activity. The antiulcer action maybe exerted through free radical scavenging mechanism.