The development of effective antisecretory drugs has risen the question of what is the ideal inhibition of gastric acid secretion in the treatment of peptic ulcer. Cimetidine, unlike the more recent H2-blockers and proton pump inhibitors, exerts antisecretory effects that are correlated to the blood levels of the drug. For this reason, therapeutic posologies were initially based on the pharmacokinetic features of the drug, while, more recently, direct measurement of intragastric acidity have assumed great relevance. Despite extensive research, the ideal level of gastric acid inhibition in the treatment of peptic ulcer has not been established. Greater healing rates are achieved by more potent antisecretory drugs and the duration of treatment appears to be also important, particularly to the healing of gastric ulcers. Whether the course of peptic ulcer disease is affected by the potency of the drug employed in the treatment of acute episodes has not been established.