1. The effect of sodium pentobarbital and Inactin anaesthesia on renal haemodynamics in the rat was evaluated with radioactive microspheres 15 μm in diameter.
2. Both anaesthetic agents caused substantial decrements in total renal blood flow (sodium pentobarbital, −34%; Inactin, −24%) compared with unanaesthetized animals.
3. Measurements of renal function obtained in rats anaesthetized with either of these anaesthetic agents should be interpreted with caution.