The effect of somatostatin was tested on gastrin release induced by electrical vagal stimulation in anaesthetized cats. The antral release of gastrin was determined in the gastric venous outflow by simultaneous recording of gastrin concentration and blood flow. Repeated vagal stimulations at the same frequency and duration caused release of similar amounts of gastrin within the same cat. Infusion of somatostatin, at a rate of 0.5 µg/kg/min, reduced the vagally induced gastrin release to about 40%. Similarly, basal gastrin output was depressed to about 40% of the control values.