The effects of 3 months' maintenance treatments with cimetidine, 400 mg at bedtime, or with carbenoxolone, 150 mg/daily, in patients whose duodenal ulcers healed after an initial course with cimetidine were compared. Carbenoxolone promoted a significant enhancement of cimetidine-altered mucus secretion, whereas in the cimetidine group no mucus recovery was found. Within 6 months from healing time 48.1% of the patients in the cimetidine group relapsed, compared with 21.4% in the carbenoxolone group. The difference is statistically significant (p < 0.05). Our results suggest that carbenoxolone maintenance is more effective than cimetidine in preventing recurrence of ulcers, being also a cheaper and shorter maintenance treatment.