We have investigated the relationship between the suppression of acidity by antisecretory drugs for the treatment of benign gastric ulcer and their corresponding ulcer-healing rates. For a variety of antisecretory drug regimens, there was a significant correlation between suppression of 24-h intragastric acidity and ulcer healing rates after 2, 4 and 8 weeks of treatment. There was a lesser degree of correlation between healing and suppression of nocturnal acidity and the association between suppression of acidity and gastric-ulcer healing rates was less marked than that previously described for duodenal ulcer.