The metabolism and renal effects of enflurane were studied during and after anesthesia in ten surgical patients without renal disease; ten control patients received halothane. Enflurane was metabolized to inorganic fluoride with a mean peak serum level of 22.2 +/- 2.8 muM four hours after anesthesia. Urinary inorganic and organic fluoride excretions were increased but oxalic acid excretion was not, suggesting that the latter is not an enflurane metabolite. Postanesthetic renal function, including the response to vasopressin, was normal in both groups. During enflurane anesthesia renal blood flow, glomerular filtration rate, and urinary flow rate were 77, 79, and 67 per cent of control values, respectively. In this study of patients without renal disease, metabolism of enflurane to inorganic fluoride was insufficient to cause clinically significant renal dysfunction.