The incidence and severity of osteopenic bone disease in primary sclerosing cholangitis is poorly defined. Clinical, biochemical and radiographic assessment and bone mineral density measurements of the lumbar spine were carried out in two groups of patients. Group 1 consisted of 30 patients with advanced primary sclerosing cholangitis; group 2 consisted of 18 patients with newly diagnosed primary sclerosing cholangitis. Only one patient had bone pain. All patients were normocalcemic; two had elevated serum parathormone levels. Fourteen patients (47%) from group 1 but no patients from group 2 had low serum 25-hydroxyvitamin D levels. Mean bone mineral density was significantly reduced in group 1 patients (0.97 +/- 0.04 gm/cm2) compared with age-matched and sex-matched controls (1.25 +/- 0.01 gm/cm2, p less than 0.0001), and in 15 patients (50%) bone mineral density was below the fracture threshold (0.98 gm/cm2). The bone mineral density in group 2 was not significantly different from controls, and no patient was below the fracture threshold. In neither group did bone mineral density correlate with serum bilirubin, 25-hydroxyvitamin D, fecal fat excretion, previous drug therapy or the presence of chronic ulcerative colitis. Histomorphometrical examination of bone from four group 1 patients showed increased bone resorption, reduced bone formation, moderate-to-severe osteopenia and no osteomalacia. In conclusion, severe osteopenic bone disease is common in advanced primary sclerosing cholangitis and, like that seen in other cholestatis diseases, is consistent with osteoporosis.