Summary. The effects of HB 699, a non-sulphonyl urea acyl-amino-alcyl benzoic acid derivative, were studied in unanaesthetized dogs. Changes in blood glucose and plasma insulin, glucagon, pancreatic polypeptide and somatostatin were measured after a single intravenous injection. HB 699 caused hypoglycaemia and stimulated insulin secretion in a dosedependent manner. The effects of lib 699 (40 mg/ kg) on pancreatic hormone secretion were compared to those of tolbutamide given at a dose (12 mg/kg) which induced a similar maximal hypoglycaemia. Both drugs caused a similar increase in insulin release (180 + 32% for tolbutamide and 240 + 41% for HB 699) lasting for approximately l hour. Despite hypoglycaemia, plasma glucagon concentrations were unaltered by either substance. HB 699 caused a marked increase in the secretion of pancreatic polypeptide (220 _+ 60% at 30 min) for up to 2 hours, whereas tolbutamide caused no significant change in plasma pancreatic polypeptide levels. In contrast, while tolbutamide caused a significant (45 + 12%) but short-lived increase in plasma somatostatin concentrations, HB 699 had no significant effect.Key words: Acyl-amino-alcyl benzoic acid derivative, hypoglycaemic agent, insulin release, pancreatic polypeptide, glucagon, somatostatin, tolbutamide, unanaesthetized dogs.Certain acyl-amino-alcyl benzoic and phenylpropionic acid derivatives were previously described as having hypoglycaemic properties [1,2,3,4]. These substances are devoid of the structural requirements regarded as essential for the insulin releasing action of hypoglycaemic sulphonamides, the sulphamidothiodiazol and sulphonylurea groups. (Fig. 1) is identical with one part of the glibenclamide molecule, a second generation hypoglycaemic sulphonamide that has been extensively studied.In vitro studies using the isolated perfused rat pancreas have shown that HB 699 stimulates insulin release without affecting glucagon release in the presence of glucose [4,5]. In the first part of the present study the effects of liB 699 on blood glucose and plasma insulin concentrations were examined in conscious dogs. In the second part of the study the effects of HB 699 on plasma glucagon, pancreatic polypepfide (PP) and somatostatin concentrations were measured. In all experiments tolbutamide was used as a reference hypoglycaemic agent.