In a double-blind study, cardiovascular parameters (cardiac output, heart rate, systolic and diastolic arterial pressure, pulmonary and systemic vascular resistances) were measured invasively in two groups of patients receiving 3 x ED90 of rocuronium or vecuronium. Measurements were made at 2, 5 and 7 min after administration and 10 and 15 min after subsequent intubation. Systemic vascular resistance mostly increased, sometimes quite markedly, although, because of the variability, rarely statistically significantly. However, heart rate, arterial pressure and cardiac output were not altered to a clinically relevant degree.