The authors present the case of three patients from the same family in whom hereditary hemorrhagic telangiectasia (HHT) or Rendu-Osler-Weber syndrome was diagnosed. The disease is rare and occurs with multiple telangiectases of the skin and mucosa, and pulmonary arteriovenous fistulae. The clinical status of our patients included multiple telangiectases of the skin and mucosa, recurrent epistaxis, exertion dyspnea and cyanosis. Polycythemia and hypoxemia were observed in the blood. The clinical status and conventional radiological examination of the thoracic region, with the suspicion of arteriovenous (A-V) fistulae, pointed to HHT. A-V fistulae were confirmed by pulmonary angiography. The pulmonary A-V fistulae were operated in all three patients and diagnosis was confirmed by histopathological examination of the operated samples. Clinical improvement was observed after the operation and cyanosis, dyspnea, hypoxemia and polycythemia disappeared.