SUMMARY1. The cardiovascular actions of dopamine have been studied in the anaesthetized dog by measuring blood pressure, heart rate, cardiac output and peripheral resistance.2. Observations with phentolamine, propranolol and haloperidol indicate that dopamine acts on α‐ and β‐adrenoreceptors, and also on specific dopamine receptors.3. In dogs pretreated with phentolamine, dopamine has a potent vasodilator action which appears to be mediated through specific dopaminergic receptors.4. Displacement of noradrenaline by dopamine is not an important component of the pressor response in the dog, and dopamine does not appear to act as a partial agonist in mediating the depressor res