In 8 experiments on anaesthetised cats bursts stimulation of the peripheral cut end of right vagus nerve leads to synchronisation of cardiac and vagus rhythms. Alterations of burst sequence frequency within definite limits has been synchronously reproduced by heart thus creating managed brady-cardia possibility. Neurotensin (4.10(-8) M intravenously) accelerate heart rate and potentiate total vagal chronotropic effect. Vagotropic effect of the neurotensin is due to enlargement of the tonic component's strength in the vagal chronotropic effect. On the other hand, extent of the synchronizing vagal influences upon heart rhythm is unaffected. Mechanisms of the participation of neurotensin in organisation of the vegetative control of the cardiac rhythm are discussed.