To describe clinical presentations of hereditary hemorrhagic telangiectasia (HHT) patients in Japan. There were 80 patients (40 men and 40 women, age 2-78, mean 39.4 years old), who were either genetically verified or genetically not identifiable but clinically definite HHT patients. Clinical presentations of these HHT patients were analyzed retrospectively. Radiological examinations, which included at least brain magnetic resonance imaging and lung computed tomography, were performed when indicated. Seventy-eight patients had either endoglin (ENG) or activin A receptor type II-like 1 (ACVRL1) mutation. They were 53 HHT1 patients with ENG mutation in 27 families and 25 HHT2 patients with ACVRL1 mutation in 17 families. Two other female patients were clinically definite HHT, but genetic mutation could not be identified. Nosebleeds were noted in 53/53 (100%) HHT1 and 24/25 (96%) HHT2 patients. Telangiectases were observed in 34/53 (64%) HHT1 and 18/25 (72%) HHT2 patients. Pulmonary arteriovenous malformations (AVMs) were noted in 33/52 HHT1 (63%) and 5/25 HHT2 patients (20%). Brain AVMs were detected in 12/51 HHT1 (24%) and 1/25 HHT2 (4%) patients. Hepatic AVMs were noted in 7/29 (24%) HHT1 and 16/20 (80%) HHT2 patients. The number of HHT1 patients was roughly twice as many as that of HHT2 patients in Japan. Pulmonary and brain AVMs were predominantly observed in HHT1 while hepatic AVMs were detected in HHT2. It seemed that ethnicity and regionality had minimal roles in the clinical presentation of HHT.