Antiulcerogenic activities of three plant drugs were studied against aspirin-induced gastric ulcers in rats. In addition, their effects on output of gastric acid and pepsin and hexosamine concentrations in gastric fluid were recorded in ulcerated and non-ulcerated rats. Solanum nigrum (aerial parts) powder and its methanolic extract decreased the ulcer index significantly. The activity may be due to inhibition of acid and pepsin secretions and/or their in vitro ability to bind these. Brassica oleracea (leaf) powder did not affect the ulcer index significantly but its aqueous extract lowered the index and increased hexosamine levels, suggesting gastric mucosal protection. Ocimum basilicum (aerial parts) powder and its aqueous and methanolic extracts decreased the index. Moreover, the acid output was decreased by its methanolic extract while hexosamine secretion was enhanced. This suggests that its antiulcerogenic effect is due to decreases of acid and pepsin outputs which enhance gastric mucosal strength. The reference drug gefarnate decreased the ulcer index by increasing the hexosamine level only. Cimetidine inhibited the acid production but did not decrease the ulcer index.