Severe hepatic vascular disease developed in two patients 4 and 8 years after kidney transplantation, while receiving combined immunosuppressive therapy with prednisone and azathioprine. Portal hypertension and marked liver failure were observed in both cases. The diagnosis was established by histological examination of liver biopsies showing typical veno-occlusive disease of the liver associated with peliosis in both cases. Azathioprine was discontinued. Two years later one patient was asymptomatic and liver function tests were normal. The second patient died 3 years later from liver failure. Early recognition of hepatic vascular disease arising in kidney transplant recipients would be of utmost importance, as substitution of another immunosuppressive agent for azathioprine could halt the process leading to portal hypertension.