M. Osler (Hereditary Hemorrhagic Telangiectasia, HHT) is an autosomal dominant inherited disease, with various vascular malformations. The genetic cause of this disease lies in different defects of transmembrane proteins (endoglin, activin receptor like-kinase 1) that can be defined as components of the receptor complex for transforming growth factor beta (TGF beta). Vascular malformations include the gastrointestinal tract and especially the liver. The location of mutations encoding hepatic involvement of M. Osler still remains unknown. These vascular malformations may lead to different shunts in the liver and can result to different complications like cardiac-insufficiency, portal hypertension and hepatic encephalopathy in adulthood. Color Doppler sonography is the method of choice for screening patients with M. Osler--suspected of having hepatic involvement. As in rare events conservative treatment of complications of hepatic involvement fail, embolization of the hepatic artery as minimal invasive therapy, surgical ligation of the A. hepatica and liver transplantation are possible treatment options. As there are only limited experiences with these therapeutic procedures patients with liver involvement should be treated at a center, where all therapy options are available.