We examined the effect of a long-term home oxygen therapy on prognosis in patients with chronic hypoxemic pulmonary diseases. The oxygen therapy group (HOT group) consisting of 33 patients and the non-oxygen therapy group (CONTROL group) consisting of 32 patients were studied. The mean observation period were 53±22 months in HOT group and 47±19 months in CONTROL group. Cumulative surviving rate curve was not significant different between HOT group and CONTROL group. In contrast the surviving rate curve in patients with pulmonary emphysema significantly higher in HOT group than in CONTROL group after 40 months, while until 40 months the curve was higher in CONTROL group. In patients with the arterial partial oxygen pressure less than 60 Torr the difference was more distinct. Effect of home oxygen therapy on prognosis was demonstrated after long term followup in patients with severe hypoxemic emphysema.