Five male patients with veno-occlusive disease of the liver (VOD) were observed in 200 consecutive renal transplants (RT) treated with azathioprine and prednisone. Mild liver enzymatic increases not justified by other reasons were detected between 2 and 9 months after RT. All 5 patients developed portal hypertension and died between 18 and 79 months following RT. Diagnosis of VOD was histological; in 3 cases diagnosis was made while the patients were still alive. In our patients, 9 previous viral hepatotropic infections (5 during hemodialysis and 4 after TR) were demonstrated. Due to the reported low incidence of VOD in RT patients, when many of them have been treated with azathioprine, the etiological role of this drug must be questioned. However, the possible association of a previous hepatotropic viral infection and the use of an immunosuppressive agent should be considered as a probable cause of VOD in kidney grafts.