Acute, sustained, moderate- to high-intensity exercise has been shown to induce significant alterations in the distribution and function of leukocytes during recovery. In many instances, these changes have been found to reflect a transient impairment of immune function in vitro during recovery from such exercise. Carbohydrate supplementation during exercise has been associated with an attenuation of cortisol production. Because cortisol has been linked to immunosuppression, a growing body of research has examined the influence of carbohydrate supplementation on immune function in response to exercise. New areas along this line of inquiry involve examination of the cytokine response to exercise and the role that carbohydrate may play in regulating the production of proinflammatory cytokines. Inter-relations among the immune response, production of specific cytokines, and cortisol are also examined. The clinical significance of an attenuated immune response when exercising as a result of the administration of supplemental carbohydrate is yet to be determined.