SMS 201-995 (5-100 micrograms) injected subcutaneously in normal and type-2 diabetic subjects 30 min before a test meal caused dose-related suppression of plasma concentrations of insulin, glucagon, and several regulatory gut peptide hormones (gastrin, gastric inhibitory peptide, pancreatic polypeptide, secretin, neurotensin, and motilin). Effective hormone suppression was achieved even at the lowest dose of 5 micrograms. In the normal subjects SMS caused postprandial hyperglycaemia, but there was no overall deterioration in glucose tolerance in the type-2 diabetic patients. This suggests that counterregulatory hormones play an important part in the metabolic disturbance of type-2 diabetes.