Oral administration of SMS 201-995 (SMS), a subcutaneously injectable somatostatin analogue, was investigated in five healthy volunteers, who drank 2 mg of SMS with 75 g of glucose. Mean maximal plasma SMS concentrations after the 2 mg oral dose were comparable with those after subcutaneous injection of 50 micrograms, although the peak was delayed (90 vs 15 min). Biological activity of absorbed SMS was shown by significant and lasting suppression of plasma insulin concentrations, resulting in significant hyperglycaemia at 90 and 120 min compared with the control study. The feasibility of oral administration of SMS may extend its use in the treatment of acromegaly and gut endocrine tumours. Other peptide hormone analogues, structurally 'protected' against enzymatic degradation, may also be active orally and thus be useful therapeutically.