1. In order to study the absorption of omeprazole under normal acidic conditions in the stomach as well as when the granules are exposed to minimal gastric acid, eight healthy males were given 20 mg omeprazole as enteric coated (EC) granules either alone or 2 h after a ranitidine dose of 300 mg, respectively. 2. Blood samples were collected at intervals for 12 h following both omeprazole administrations. The pH was recorded during the first 4 h in half the subjects in each experiment to document the difference in pH during the absorption phase of omeprazole. 3. The area under the plasma concentration-time curve, AUC, of omeprazole was virtually the same irrespective of whether or not the granules were exposed to gastric acid. However, the maximum plasma concentration (Cmax) was higher and the time to reach Cmax was shorter when omeprazole was administered after a ranitidine dose. 4. It is concluded that gastric acidity has negligible influence on the AUC of omeprazole, which is directly correlated to the antisecretory effect, when administered as EC granules.