The trial randomly assigned 652 patients with non-ulcer dyspepsia (NUD), defined as chronic or recurrent complaints of acid-related (heartburn, acid regurgitation, epigastric pain) and non-acid related (fullness/vomiting, nausea) symptoms and with no evidence of organic disease, to treatment for 4 weeks with 150 mg of ranitidine (Zantic, CAS 66357-59-3) twice a day, or placebo, according to a double-blind design. The presence and duration of all dyspeptic symptoms were recorded by interviews at the beginning and after 2 and 4 weeks of treatment as well as by diaries. The complete disappearance of all dyspeptic symptoms after 4 weeks in the placebo group was 36%; ranitidine treatment resulted in a significant improvement after 4 weeks (p < 0.05). The effect of ranitidine was slightly more pronounced in acid-related than in non-acid-related symptoms. We conclude that suppression of gastric acid secretion is of clinical value in NUD patients, especially in those suffering from epigastric pain, acid regurgitation and heartburn.