Three cases of azathioprine-induced complex of liver diseases are described, and their light microscopy and ultrastructural findings are detailed. It was found that the drug produces a spectrum of pathological changes that include veno-occlusive disease, peliosis hepatis, perisinusoidal (Disse space) fibrosis, and nodular regenerative hyperplasia. It is suggested that the explanation for this spectrum is the variable degree of damage to the endothelial cells lining the sinusoids and the terminal hepatic venules. This spectrum is seen almost exclusively in male patients with renal transplant.