Pancuronium, vecuronium and a combination of these were administered in an incremental fashion to study any potentiation of effect with the combination of the two relaxants. The ED95 (dose producing a 95% block) of the combination was 29 micrograms kg-1 for each component in comparison to 57 micrograms kg-1 for vecuronium and 59 micrograms kg-1 for pancuronium. The dose-response curves for the three groups did not differ from each other and no potentiation was demonstrated.