Gallamine triethiodide causes tachycardia thought to be due to a specific vagolytic action. Recently, Brown and Crout have shown that gallamine may cause increased inotropic and chronotropic activity due to the release of catecholamines from cardiac sympathetic nerves. As a further analysis of the mechanisms, experiments were performed on pithed rats and spinally transected, braindestroyed catsin vivo pretreated with hexamethonium and/or propranolol to determine the nature of the antiacetylcholine action of gallamine on the heart.