Ranitidine disposition has been studied in 12 patients with renal impairment following 50 mg given intravenously and 150 mg given by mouth on separate occasions. The clearance of ranitidine from plasma (y) was correlated with creatinine clearance (x): y = 10.47 + 0.289x,r2 = 0.751, but there was no significant correlation of creatinine clearance with distribution volume or bioavailability. The mean (s.e. mean) distribution volume was 1.62 (0.08) 1/kg and the mean bioavailability 0.81 (0.05). These data suggest that in order to obtain similar ranitidine plasma concentrations in anephric patients and patients with normal renal function, the maintenance dose in the anephric patients should be 25-30% of that for patients with normal renal function.