The cardiovascular effects of Org 9487 during isoflurane anaesthesia have been evaluated using three doses around its ED90 for neuromuscular blockade, i.e. 1 mg kg−1, 2 mg kg−1 and 3 mg kg−1. Heart rate increased to 110%, 115% and 118% in patients receiving 1 mg kg−1, 2 mg kg−1 and 3 mg kg−1 respectively. There were no significant effects on systolic and diastolic blood pressures for the two lower dose groups. Patients receiving Org 9487 3 mg kg−1 displayed significant decreases in systolic and diastolic blood pressures (91% and 82% of the control values respectively). Except for heart rate in the group receiving 3 mg kg−1, all measurements returned to baseline after a maximum of 15 min. Six patients experienced a transient increase in airway pressure after administration of Org 9487, which was accompanied by a decrease in oxygen saturation in two out of six subjects, but there was no audible wheezing. These episodes were self-limiting and required no treatment. There were no other adverse reactions to this drug during this study.