A new aminosteroidal neuromuscular blocking agent, rocuronium bromide, has recently been introduced into clinical practice. Its main advantage over other currently used drugs of this kind is its fast onset of action, which could render rocuronium the muscle relaxant of choice for rapid facilitation of tracheal intubation. A further advantage of the new compound over vecuronium bromide is the less extensive formation of breakdown products, reducing the contribution of active metabolites to the neuromuscular blocking effects of the parent compound.Thorough knowledge of the pharmacokinetics of any new drug is highly desirable for the anaesthesiologist because absorption, distribution to the tissue, as well as elimination by biotransformation and excretion, are closely related to its effects. Due to its chemical relationship to other aminosteroidal neuromuscular blocking agents such as pancuronium bromide or vecuronium, rocuronium is expected to display pharmacokinetic behaviour similar to that of its predecessors. Hepatic and renal disease may prolong the effect of rocuronium, but to a lesser extent than seen with pancuronium or vecuronium, because the plasma clearance of rocuronium is not significantly influenced by dysfunction of the liver or kidneys. On the contrary, in elderly or hypothermic patients the reduction in plasma clearance results in a prolonged duration of the action of rocuronium.All information on the pharmacokinetics of this new nondepolarising neuromuscular blocking agent which has been made available to date is presented in this review, with a discussion of the significance of these data for clinical use of the drug.