Before now, there has been no study of finasteride use exceeding 1 year in Japanese men with androgenetic alopecia (AGA) except the study subsequently conducted from the development phase. Since the launch of finasteride, no study in a larger population had been reported. Ethnic variation of the onset age, progressive nature and degree of hair loss of androgenetic alopecia are known. The therapeutic effect of oral finasteride (Propecia) was examined on androgenetic alopecia of Japanese men. The efficacy and safety of finasteride (1 mg tablet) was evaluated in Japanese men with AGA in the long term. The study enrolled 3177 men given finasteride 1 mg/day from January 2006 to June 2009 at our clinic. Efficacy was evaluated in 2561 men by the modified global photographic assessment; the photographs were assessed using the standardized 7-point rating scale. Safety data were assessed by interviews and laboratory tests in all men enrolled in the study. The overall effect of hair growth was seen in 2230 of 2561 men (87.1%), in whom hair greatly (11.1%), moderately (36.5%) and slightly (39.5%) increased. The response rate improved with increasing duration of treatment. Adverse reactions occurred in 0.7% (23/3177) of men; seven men discontinued treatment based on risk-benefit considerations. No specific safety problems associated with long-term use were observed. This study represents data collected at a single institution. Many patients did not receive follow-up examination. In Japanese men with AGA, oral finasteride used in the long-term study maintained progressive hair regrowth without recognized side-effect.