It has been postulated that altered hepatic blood flow, particularly reduced portal flow, is responsible for the induction of hyperplasia of liver cells and nodule formation. This report describes the case of a 31-year old female patient developing multiple focal nodular hyperplasia (FNH) lesions two years after portocaval shunting and extended right hemihepatectomy due to the suspicion of a malignant liver tumor. Portocaval shunting became necessary due to iatrogenic thrombosis of the entire portal vein after preoperative embolization of the right portal vein. This observation provides for the first time direct evidence for the pathogenesis of FNH in humans.