The purpose of this study was to evaluate nutritional therapy for non-insulin-dependent diabetic subjects by examining the changes in, and interrelationship of, the outcome criteria of efficacy, namely, blood glucose, body weight and serum lipids, total cholesterol, and triglycerides. Eight-two patients, who represented all those seen by one nutritionist at a diabetic education center, were contacted for long-term follow-up data, which was obtained on 80.5% of the patients. They had short-term follow-up 66.0 +/- 4.5 days after the initial visit and long-term follow-up 31.0 +/- 1.1 mo later. Four treatment groups were defined: group 1, diet only at entry and follow-up; group 2, oral hypoglycemic agents at entry and follow-up; group 3, intensified treatment (diet or oral agents at entry and oral agents or insulin at follow-up; and group 4, decrease in intensity of treatment (oral agents at entry but not at long-term follow-up). Serum glucose fell significantly (P less than 0.05) at short- and long-term follow-up in groups 1, 2, and 3. Body weight reductions were significant at short-term follow-up in all groups and were significant at long-term follow-up only in group 1. Serum cholesterol was significantly reduced at short-term follow-up in group 2. Serum triglyceride changes were significantly reduced at short-term follow-up in groups 1 and 2 and at long-term follow-up in group 1. Serum glucose changes correlated with changes in serum cholesterol and triglycerides but did not correlate with body weight changes. These findings demonstrate the effectiveness of nutritional counseling, show that lowering serum glucose did not correlate with weight reduction, and suggest that more attention should be given to factors reducing serum glucose and less attention to weight loss in the treatment of non-insulin-dependent diabetes.