A case of prolonged apnea after administration of succinylcholine in a patient homozygous for the dibucain variant cholinesterase (genotype E1aE1a) has been presented. Knowledge of the patient's medical history, preoperative laboratory tests, and the length of apnea enabled the surgical team to eliminate liver disease, carcinoma, and malnutrition from the differential diagnosis. This, in addition to the patient's failure to respond to an anticholinesterase agent, led to the belief that the patient had an atypical cholinesterase response to succinylcholine and not one secondary to a decreased production of cholinesterase enzyme from an impaired liver or prolonged paralysis for the nondepolarizing agent, pancuronium. Treatment consisted of maintaining adequate pulmonary ventilation nitrous oxide sedation to diminish anxiety until the patient regained spontaneous respiration. Anticholinesterase agents were used after the patient had progressed to a phase II depolarization block. After a cholinesterase assay of the family's serum, all members having the atypical allele were instructed to obtain medical alert identification.