SUMMARYLansoprazole (AG 1749/CG 4801) is an inhibitor of gastric acid secretion by blocking H+,K+‐ATPase. In this 2:1 randomized, double‐blind, multicentre trial lansoprazole 30 mg am was compared to 40 mg famotidine nocte in 264 out‐patients suffering from uncomplicated duodenal ulcer. After 2 weeks of treatment ulcer healing was confirmed endoscopically in a significantly higher proportion (P= 0.027) of patients treated with lansoprazole (94/174 = 54.0%) compared to patients receiving famotidine (35/90 = 38.9%). Cumulative healing rates after 4 weeks were 91.4% for the lansoprazole group and 83.3% for the famotidine group (P= 0.065). Pain relief and decrease of concomitant antacid consumption during treatment were comparable in both groups. Both compounds were well tolerated. Rates of recurrent duodenal ulcer in the 6 months after trial treatment were 45/158 (28.5%) after lansoprazole, and 18/69 (26.1%) after famot