In the last years the importance of the evaluation of antacid compounds according to their neutralizing capacity decreased. Clinical investigations have shown that antacid mixtures of aluminum-magnesium hydroxide healed gastric an duodenal ulcers (neutralizing capacity 100-150 mmol/day) as well as H2 receptor antagonists and better than a placebo. By this the necessary daily dosage could be reduced essentially. This paper presents studies showing that lattice like structured antacids (e.g. Magaldrate) healed gastric and duodenal ulcers (neutralizing capacity 100-350 mmol/day) as well as Ranitidine (150 mg b.d.). Maintenance therapy should be evaluated critically because sufficient data are not available and mineral metabolism is changed significantly by extremely small dosages of aluminium-magnesium hydroxide antacids even in patients with normal kidney function.