Preliminary data indicated that viscous fiber (guar) and alpha-glycosidase inhibition (acarbose) used in combination to slow carbohydrate absorption have an apparently additive effect in reducing the postprandial glycemic response. The full endocrine data reported here also demonstrate that reductions in insulin and gastric inhibitory polypeptide are most significant when guar and acarbose are used in combination. The results are divergent for enteroglucagon when guar and acarbose were given singly. Raised enterglucagon levels seen after acarbose are in keeping with inhibition of proximal absorption resulting in more distal absorption of carbohydrate. However, with viscous fiber, the enteroglucagon response was reduced, and this reduction was maintained even after addition of acarbose. The results demonstrate that the gut endocrine response can be manipulated by pharmacological interventions which alter the pattern of carbohydrate absorption.