Evidence suggests that diet and exercise are associated with improved glucose tolerance for patients with non-insulin-dependent diabetes mellitus (NIDDM). Seventy-six volunteer adult patients with NIDDM were each assigned to one of four programs: diet, exercise, diet plus exercise, or education (control). Each program required ten weekly meetings. Detailed evaluations were completed prior to the program and after three, six, 12, and 18 months. Evaluations included various psychosocial measures, measures of the quality of life, and fasting blood glucose, glycosylated hemoglobin, and relative weight determinations. Of the 76 original participants, 70 completed the 18-month follow-up study. At 18 months, the combination diet-and-exercise group had achieved the greatest reductions in glycosylated hemoglobin measures. In addition, this group showed significant improvements on a general quality of life measure. These improvements were largely uncorrelated with changes in weight. The authors conclude that the combination of dietary change and physical conditioning benefits NIDDM patients, and that the benefits may be independent of substantial weight loss.