BACKGROUND: Because of the widespread use and availability of agricultural insecticides, acute organophosphate poisoning as a suicide or an accident is becoming the most common type of poisoning and serious problem in Korea. The mortality of organophosphate poisoning varied from 10 to 86 percent. The cause of death was thought to be a combination of excessive bronchial secretion, bronchospasm, respiratory muscle paralysis and depression of respiratory center, summarily respiratory failure. We evaluated the respiratory complications in patients with acute organophosphate intoxication to determine the predisposing factors to respiratory failure and to reduce the incidence of respiratory failure or mortality. METHOD: We conducted a retrospective study of 111 patients with the discharge diagnosis of organophosphate poisoning who were hospitalized at Yenugnam University Hospital during the 5 years. The diagnosis of organophosphate poisoning has based on the followings (1) a history of exposure to an organophosphate compounds. (2) the characteristic clinical signs and symptoms. (3)decrease in the cholinesterase activity in the serum. RESULTS: The results were as follows 1) Respiratory failure developed in 31(28%) of 111 patients with acute organophosphate poisoning. All cases of respiratory failure developed within 96 hours after poisoning and within 24 hours in 23 patients. 2) The 80 patients who did not develop respiratory failure survived. In 31 patients with respiratory failure, 15(44%) patients were dead. 3) The patients with respiratory failure had more severe poisoning, that is, the lower level of serum cholinesterase activity on arrival, the higher mean dosage of atropine administered within first 24 hours. 4) In 16 patients with pneumonia, 14 patients developed respiratory failure. In 5 patients with cardiovascular collapse, 2 patients developed respiratory failure. 5) There was no correlation to between age, sex, the use of pralidoxime and respiratory failure. 6) The serum cholinesterase level in survivors at time of respiratory failure and weaning was 66.05+/-85.48U/L, 441+/-167.49U/L, respectively. CONCLUSION: All the respiratory failure complications of acute organophosphate poisoning occurred during the first 96 hours after exposure. The severity of poisoning and pneumonia were the predisposing factors to respiratory failure. Aggressive treatment and prevention of the above factors will reduce the incidence of respiratory failure.