Succinylcholine is a depolarising muscle relaxant that is used for rapid tracheal intubation in general anesthesia. It is a short-acting drug which is hydrolyzed by plasma cholinesterase. Some factors can decrease the activity of this enzyme in body. Some patients may have abnormal form of this enzyme that leads to prolonged duration of action and apnea. The subjects of this research were a male (55) and a female (57) who had prolonged apnea after administration of succinylcholine (4-8h), and they improved completely after mechanical ventilation.