Atracurium and Cis-atracurium are the muscle relaxants of choice in both liver and renal failure. Atracurium is inactivated by Hoffman's elimination and alkaline ester hydrolysis. Cis-atracurium is eliminated by Hoffman's elimination. Hence atracurium and cis-Atracurium duration of action is not altered in patients with hepatic or renal insufficiency or hemodynamic compromise .Therefore, preferred muscle relaxants for such patients as well as for neonates and elderly.