Cardiovascular effects of Org NC 45 and pancuronium were examined in seven anaesthetized dogs. Systemic circulatory effects were measured after increasing doses administered as a single i.v. bolus. Cardiac effects were measured after intracoronary (i.c.) injection of the equivalent dose of the respective neuromuscular blocking agent, which produced 90% neuromuscular blockade. Org NC 45 i.v. did not cause any significant cardiovascular changes, whereas pancuronium i.v. produced significant and dose-related increases in heart rate, left ventricular (LV) dP/dtmax and cardiac output (CO). After i.c. injection of equipotent doses, neither drug induced any significant change in haemodynamic measurements. This implies that neither drug exerted a direct influence on cardiac contractility, the increases in LV dP/dt max and CO following pancuronium being dependent on heart rate.