SUMMARY1. The influence of practolol (a proposed β1‐adrenoreceptor antagonist) upon the pressure‐flow relationships in the peripheral circulation was studied in eight anaesthetized dogs during right heart by‐pass procedures.2. Practolol (1 mg/kg) produced a significant increase in the resistance to venous return which resulted in a significant fall in venous return.3. There was no significant change in arterial resistance.4. This study suggests that practolol should not be classified as an exclusive cardioselective β‐adrenoreceptor a