Partial diversion of bile flow to an external stoma was performed in 6 patients with chronic intrahepatic cholestasis with severe pruritus that had been refractory to medical measures. Four patients with progressive intrahepatic cholestasis and 2 with arteriohepatic dysplasia were treated. Follow-up has been 3-8 yr. Patients with progressive intrahepatic cholestasis have been free of itching since surgery. Serum bile salt concentrations fell from 218-275 microM (normal less than 10) before to less than 10 microM after surgery. Biochemical tests of liver function and histology returned to normal or near normal. Patients with arteriohepatic dysplasia had persistent mild pruritus after surgery. Serum bile salt concentrations fell from 153-317 to 25-37 microM. There was little or no improvement in biochemical tests or histology. Bile volume and bile salt diverted were higher in patients with progressive intrahepatic cholestasis (7.3-13.0 ml/kg.day and 83-137 mumol/kg.day, respectively) than those with arteriohepatic dysplasia (3.2-4.5 ml/kg.day and 21-36 mumol/kg.day). The quality of life since surgery has been excellent in patients with progressive intrahepatic cholestasis, but not as optimal in those with arteriohepatic dysplasia. These findings suggest that partial external biliary diversion can provide effective relief from pruritus and perhaps reversal of liver disease in patients with progressive intrahepatic cholestasis. It should be used in patients with arteriohepatic dysplasia only in those with disabling pruritus.