The purpose of this study was to assess the long-term effects of a high-complex-carbohydrate, high-fiber, low-fat diet and exercise on 69 NIDDM patients. During the initial 26-day program, fasting glucose was reduced from 179.5 +/- 10.6 to 133.5 +/- 4.0 mg/dl. This decrease in fasting glucose was achieved along with the discontinuation of oral hypoglycemic agents in 24 of 31 patients and of insulin in 13 of 18 patients; one patient was placed on insulin. Serum cholesterol and triglycerides were reduced by 25% and 27%, respectively. At 2-3 yr of follow-up, fasting glucose was not significantly different from the value observed at the end of the 26-day program. Compared with the end of the 26-day program, seven more patients were taking oral agents and four more were on insulin. Exercise and diet inventories obtained at follow-up indicated good compliance to the program and also indicated that the main difference between those patients who went back on medication at follow-up compared with those remaining off medication was the percent of calories derived from fat.