We evaluated the clinical background of type 2 diabetes mellitus patients with favorable glycemic control (HbA1c<7 %). The patients were stratified into 3 groups based on their HbA1c concentration at the time of their first visit to participating JDDM sites: Group I (<7 %), Group II (7 to <8 %), and Group III (≥8 %). We then compared the characteristics of the groups, prevalence of concomitant diseases, and the differences in their treatment. The duration of diabetes in the three groups was approximately 11 years. Group III was younger and more obese rather than Groups I and II. We therefore hypothesized that Group I included cases of diabetes mellitus that were originally mild along with cases in which favorable glycemic control had already been obtained with previous treatments. In Groups II and III, the mean HbA1c concentration reached ≤7 % after 1 year of treatment at the participating JDDM sites. The prevalence of retinopathy and nephropathy in Group I was less than that in Group III. The proportion of cases in which favorable glycemic control was maintained with diet and exercise was high in Group I. The HbA1c concentration at the first visit influenced the clinical features in the present study. The results show the importance of achieving glycemic control at the early stage of diabetes.