To develop an instrument to measure the quality of life (QOL) in Japanese patients with type 2 diabetes, we evaluated the Diabetes Quality of Life (DQOL) Scale developed for the Diabetes Control and Complications Trial (DCCT) and translated into Japanese with the permission of the DCCT Research Group. Subjects were 239 outpatients 40 years and over at Jikei University Hospital, studied to assess the instrument's reliability and validity. Using the 40 questions in the DQOL, we reconstructed the questionnaire by factor analysis. Four newly detected factors are interpreted as the domains of “limitation on daily life, ” “overall satisfaction, ” “psychological burden, ” and “satisfaction with treatment.” Cronbach's alpha coefficients indicated that the instrument was internally consistent (alpha=0.73 to 0.92). The four domains of the instrument mutually correlated. Our findings suggest that the instrument is useful for assessing QOL in patients with type 2 diabetes in Japan, although further revision may be necessary.