A 45-year-old man with hereditary hemorrhagic telangiectasia (HHT) presented with numerous mucocutaneous telangiectases, recurrent nosebleeds, and several first degree relatives with similar symptoms. HHT has been linked to mutations in the genes endoglin and activin receptor-like kinase-1 (ALK-1), which are located on chromosome 9q33-34 and 12q13, respectively. The resultant proteins mediate binding and signaling of transforming growth factor-beta. The clinical features, molecular basis, and management of HHT are reviewed.