Totally isolated whole canine stomachs perfused, ex vivo, with homologous blood of living supporting dogs were used for recording of myoelectrical mechanical activities. Drugs were administered directly into the arterial system of the isolated stomachs either as flash injections or as constant infusions. Flash injection of metoclopramide (Maxeran) led to the response activity (spiking) and associated mechanical response. Electrical control activity was also affected by Maxeran: the changes consisted of premature control activity and uncoupling. Similar reactions were observed after flash injections of methacholine, pentagastrin or electrical stimulation of the Latarjet nerve. These reactions were dose-dependent. Tetrodotoxin, atropine, hexamethonium and glucagon, when given as a constant infusion, did inhibit the action of Maxeran on myoelectrical and mechanical activities of the isolated stomach. Inhibition of the responses to Maxeran by atropine and tetrodotoxin implicates acetylcholine in the mediation of these responses. The ability of hexamethonium to diminish the response to Maxeran suggests that a locus of action may be at both pre- and post-ganglionic sites of the intramural plexus. Exact receptors of this action are not demonstrated by this study.