The effect of long acting somatostatin analogue, SMS 201-995, on postprandial dumping syndrome was studied in eight patients with Billroth II gastric resection. Each patient was subjected to two oral glucose challenges with 75 g glucose. One challenge was premedicated with 50 micrograms SMS 201-995 subcutaneously 15 min before the oral intake of glucose, the other with placebo. With placebo all patients experienced the subjective symptoms of the early dumping syndrome with significant (P less than 0.001) increases (mean (s.d.)) in pulse rate (from 66 (8) to 102 (10) beats/min), in packed cell volume (from 0.36 (0.05) to 0.43 (0.1) l/l) and in the plasma levels of vasoactive intestinal polypeptide (from 3.0 (0.5) to 10.2 (1.8) pmol/l). During the somatostatin study the subjective symptoms and the changes in the various parameters were not detected. In the control study seven patients showed postprandial hypoglycemia. In these patients significant elevations (P less than 0.001) in the insulin level (from 10 (0.9) to 40 (9.1) microE/ml) and gastric inhibitory peptide (GIP) concentration (from 100 (13) to 220 (41) ng/l) were seen, compared with the initial values. During the application of SMS 201-995 hypoglycaemia did not develop and plasma insulin and GIP concentrations remained unchanged. These results indicate that the long acting somatostatin analogue alleviates the symptoms of early and late postprandial dumping syndromes.