The effect of chilli powder and its pungent ingredient capsaicin on gastrointestinal transit in the rat was studied. Fasted unanaesthetized male Sprague-Dawley rats (n = 144) received by gavage a test meal containing charcoal and cellulose in water or capsaicin solvent plus 51Cr as a radioactive marker. Either 100 or 200 mg of chilli powder (containing 0.13 and 0.26 mg of capsaicin, respectively) or 0.5 or 1 mg of capsaicin were added, the final volume of each meal being 1.5 mL. At 10 and 20 min, animals were killed and the amount of isotope that had left the stomach was measured, together with the distance the charcoal column had travelled along the small intestine. Compared to controls, animals given chilli powder emptied less of their gastric content at 10 and 20 min, an effect partly reproduced by capsaicin. However overall gastric-small intestinal transit was unaffected by chilli powder or capsaicin. Another 12 male Sprague-Dawley rats received, under light ether anaesthesia, on six occasions at 1-2 week intervals, the same six test meals as used in the previous experiment except that charcoal was not used. Total gut transit as measured by the amount of radioactive marker excreted in the stools at 18 and 24 h was unaffected by the use of chilli or capsaicin.