Dietary fiber consumption has been associated with a decrease in diabetes and atherosclerotic diseases in population surveys. The contribution of soluble fiber (compared to insoluble fiber) to each of these problems has been investigated in several ways. This paper reviews the role which soluble fiber consumption plays in carbohydrate and lipid metabolism. The effects of specific fibers on glucose and insulin responses are examined; possible mechanisms responsible for the described effects are discussed. Epidemiologic evidence that consumption of foods containing soluble fiber contributes to decreased atherosclerotic disease is reviewed. Studies of administration of soluble fiber to hyperlipidemic males and females and normolipidemic subjects are examined with respect to changes in plasma lipids. Soluble fiber appears to play an important role in preventing and possibly treating diabetes and hyperlipidemia, diseases common to Westernized countries.