In 20 male patients with various gastrointestinal disorders, gastric acid secretion was studied, once following administration of pentagastrin, 6μg/kg of body weight, and once following administration of betazole hydrochloride, 1.5 mg/kg, each injected subcutaneously. The peak responses to the two stimulants were not significantly different and were strongly correlated. The peak response to pentagastrin was more rapid in onset and less sustained than the response to betazole. Pentapeptide produced fewer side effects.