We studied 50 Japanese patients who were first diagnosed with type 2 diabetes mellitus. Psychological functioning was assessed by using the Rorschach test and the Yatabe-Guilford Personality test. Analysis indicated that patients who discontinued clinic attendance during the 2-yr. study period had more depression, lower general activity and less extraversion, more negative self-attitudes, and more concern about being helpless than those who continued having regular followups. This study also found that patients who had worse glycemic control 2 yr. after being first diagnosed reported more inferiority feelings, lower general activity, more need for closeness to others, and more emotional demands than those who had better glycemic control. In conclusion, understanding the psychological functioning would be helpful in the management of Japanese patients with type 2 diabetes mellitus.