This study was designed to evaluate the safety and estimate the efficacy of oral budesonide in patients with primary sclerosing cholangitis (PSC). Twenty-one patients with PSC were treated with 9 mg daily of oral budesonide for 1 yr. Significant, but marginally important, improvement in serum alkaline phosphatase (1,235 +/- 190 vs 951 +/-206 U/L, p = 0.003) and AST levels (119 +/- 14 vs 103 +/- 19 U/L, p = 0.02) was noted at the end of the treatment period. Serum bilirubin levels increased significantly in the 18 patients who completed 1 yr of treatment (1.1 +/- 0.1 vs 1.4 +/- 0.3, p = 0.01) and no significant changes in liver tests were noted 3 months after budesonide was discontinued. The Mayo risk score did not change significantly, and although a significant improvement in the degree of portal inflammation was noted at the end of the treatment period, the degree of fibrosis and stage of disease were not significantly affected. There was a marked loss of bone mass of the femoral neck (0.851 +/- 0.02 vs 0.826 +/- 0.02 g/cm2, p = 0.002) and lumbar spine (1.042 +/- 0.02 vs 1.029 +/- 0.02 g/cm2, p = 0.09) at 1 yr of treatment with budesonide. Two patients required evaluation for liver transplantation during treatment, and two patients developed cosmetic side effects. Oral budesonide appears to be of minimal, if any, benefit and it is associated with a significant worsening of osteoporosis in patients with PSC.