In a multicentre study, 146 peptic ulcer patients who had recently healed with H2 antagonists (38 gastric, 108 duodenal ulcers) received randomly for a year one of the following mucosal protecting antiulcer drugs: aceglutamide aluminium salt (AAL), zinc acexamate (ZAC) and magaldrate (MAG). Forty six patients received AAL (700 mg bid), 50 patients received ZAC (300 mg at single nocturnal dose) and 50 patients received MAG (800 mg bid). An endoscopic examination was performed at the beginning of the study and 12 months later. Clinical examinations where performed on months 3, 6 and 9, advancing the endoscopical control in case of ulcer symptoms. ZAC showed to be superior to MAG (p less than 0.05, chi-square test) in preventing relapses, with a favourable tendence in front of AAL, but without reaching statistical significance. Its important to mention the high number of withdrawals and the good tolerance of the treatments.