To study the effects of acute and chronic cholestasis on vitamin D metabolism we investigated six cases of acute extrahepatic obstructive jaundice and eight cases of primary biliary cirrhosis (PBC) (three supplemented with vitamin D). Plasma 25-hydroxyvitamin D (25OHD) was low in the patients with PBC unsupplemented with vitamin D but normal in obstructive jaundice. None of the patients with PBC showed radiological or histological evidence of osteomalacia. In PBC, dietary intake of vitamin D was low but response to ultra-violet irradiation of the skin was normal even in those with a considerably raised serum bilirubin. Patients with PBC or obstructive jaundice had low levels of 25 hydroxyvitamin D binding protein which correlated with the serum albumin. The half-life of intravenously injected (3)H vitamin D(3) ((3)HD(3)) and the subsequent production of (3)H 25OHD were normal in all the patients with obstructive jaundice and in most with PBC. The two patients with PBC who produced less (3)H 25OHD than expected were receiving vitamin D supplements. The urinary tritium ((3)H) excretion after the injection of (3)HD(3) correlated with the serum bilirubin. After the injection of (3)H 25OHD(3) the urinary excretion of (3)H was minimal and did not correlate with the serum bilirubin, suggesting that the radioactivity appearing in the urine after the (3)H vitamin D(3) injection was associated with vitamin D metabolites other than 25OHD. Factors contributing to the low plasma 25OHD in primary biliary cirrhosis may be a low dietary intake of vitamin D, inadequate exposure to ultra-violet light, and a tendency to urinary wastage of vitamin D metabolites.