In order to examine the contribution of renal papilla to atrial natriuretic factor (ANF)-induced diuresis, clearance studies were done in rats with intact papillae and bromoethylamine hydrobromide (BEA)-induced papillary necrosis. Papillary necrosis did not attenuate the diuretic and natriuretic response to ANF. In a moderately hydropenic state, urine flow and fractional water excretion were rather more increased in papillary necrosis rats than in papilla-intact ones. In a volume-expanded state, both groups had a similar diuretic response to ANF. Present data indicate that the existence of intact renal papilla is not essential for ANF-induced diuresis. Furthermore, it is suggested that absolute magnitude of ANF-induced diuresis may be dependent on its extrapapillary action(s).