A radiotelemetric technique for monitoring canine gastrointestinal function with clinical and research applications is described. Continuous gastrointestinal pH profiles for base-line (fasted) and postprandial states were recorded for a 6-hour test period in 4 Beagles, using a radiotelemetric device (Heidelberg capsule). Base-line gastric pH values were between 0.9 and 2.5 during the first 30 minutes, with a mean +/- SEM of 1.5 +/- 0.04. Postprandial gastric pH values varied between 0.5 and 3.5 during the first 30 minutes, with a mean of 2.1 +/- 0.04. Base-line duodenal pH values during the initial 5 minutes after gastric emptying varied from 4.5 to 7.5 with a mean of 6.1 +/- 0.1, and for the initial 60-minute post-gastric emptying, pH ranged from 4.5 to greater than 8.0 (beyond capsule calibration limit) with a mean of 6.7 +/- 0.05. The pH tended to increase linearly with time during the initial 60 minutes in the intestine. Mean gastric residence time of the capsule was 74 +/- 26.5 minutes in the fasted state (range 0 to 240 minutes). Postprandially, the capsule remained in the stomach for the duration of the 6-hour observation period.