Pulmonary arteriovenous malformation (PAVM) is an uncommon but not rare disease. It is very often associated with hereditary hemorrhagic telangiectasia (Osler-Weber-Rendu disease, OWRD). Both conditions may be readily diagnosed at the bedside when careful attention is given to clues from history taking and physical examination. Sometimes the clinical features may be neglected, delaying the diagnosis. The natural history of this disease is still incompletely understood because of the paucity of cases. This retrospective study was undertaken to evaluate the clinical manifestations and treatment options in patients with documented PAVM at the National Taiwan University Hospital between 1985 and 1997. Ten patients (4 men, 6 women) of documented PAVM were evaluated. Mean age at diagnosis was 37.8 years (range 22-63). Presenting symptoms included dyspnea on exertion, characteristics of OWRD, and major neurologic events. Six episodes of brain abscess occurred in three patients. The predominant location of PAVMs was the lower lobe. Solitary PAVM was more frequent in our patients (5/6) with OWRD than in other reports. The therapeutic options were: surgical resection (3 patients), embolotherapy (4), and no treatment (4). One patient, who refused treatment at first, developed a brain abscess later. There was no documented recurrence or growth of new PAVMs in patients who underwent surgical resection. Embolotherapy failed in one patient; no recanalization was found in the remaining patients. In conclusion, the diagnosis of PAVM may be subtle, but careful attention to historic clues and physical findings may lead to early diagnosis. Appropriate treatment is mandatory and may prevent the severe complications of PAVM. The debate about the preferred treatment seems likely to continue until more is known about the natural history of this disease.