The effect of test meal temperature on the gastric emptying of 500 ml of 5% dextrose containing 12 MBq of 99mTechnetium-sulfur colloid was studied in eight healthy volunteers using a quantitative scintigraphic technique. Four different temperatures, 4, 20, 37 and 55 degrees C, were investigated in random order. Gastric emptying of the test meal at each temperature was mono-exponential and measurable as a half-life. The half-life of the meal at 20 degrees C (median, 35.6 min; range, 21.7-62.6 min) did not differ significantly (P greater than 0.10) from that obtained at 37 degrees C (median, 34.3 min; range, 20.1-60.5 min). In comparison to 37 degrees C, the half-life was longer for meals at 4 degrees C (median, 48.9 min; range, 20.9-77.5 min) and at 55 degrees C (median, 60.7 min; range, 33.5-79.0 min) although statistically different only at 55 degrees C (P less than 0.01). These results confirm the view that liquid meals, colder or warmer than body temperature have an inhibitory effect on gastric emptying and show that a significant delay in gastric emptying of liquids is obtained only with a warmer meal.