Gastrointestinal pH and regional intestinal transit times of a capsule were measured in twelve healthy children aged 8-14 years using a radiotransmitting pH-sensitive capsule. The location of the capsule was determined by fluoroscopy. pH in the stomach was 1.5, but rose to 6.4 in the duodenum (mean values). pH gradually rose in the small intestine and reached an alkaline peak value of 7.4 in the distal part. pH dropped to 5.9 in the cecum but rose to 6.5 in the rectum. Median gastric residence time of the capsule was 1.1 h. Small intestinal transit time was 7.5 h, and colonic transit time was 17.2 h. pH profile and intestinal transit times found in the present study are almost identical to values found in studies on healthy adults. It is therefore concluded that the release pattern of pH-dependent sustained-release tablets in children is likely to be equal to that of adults.