Diabetes takes an enormous human and monetary toll each year. Current treatment too often revolves around insulin and drug therapy, neglecting diet and exercise. A comprehensive review was undertaken to assess and summarize the effects of dietary fiber on diabetes. Fiber supplement studies with guar, wheat bran, and apple fiber produced mixed results; some studies reported lowered fasting glucose and cholesterol values and less glycosuria. However, many available fiber supplements cause side effects. High-carbohydrate, high-fiber diets providing 55% to 60% of energy as carbohydrates, 15% to 20% as protein, and 20% to 25% as fat and including 50 gm or more fiber daily hold the most potential for long-term use. These diets reduce insulin requirements, improve glycemic control, lower fasting serum cholesterol and triglyceride values, and promote weight loss. Studies show good long-term adherence with these diets. Dietitians assume primary responsibility for educating individuals on the benefits and use of high-carbohydrate, high-fiber diets. Diets must be individualized, with special modifications for obesity, hyperlipidemia, or physiological states such as pregnancy and lactation. Widespread use of high-fiber diets will ultimately improve metabolic control and decrease health care costs for thousands of diabetic and non-diabetic individuals.