Paraquat poisoning is often observed in agricultural regions, and the prognosis is very poor even with intensive treatment, including direct hemoperfusion. Prognostic factors for paraquat poisoning were analyzed in 36 cases we experienced during the past 18 years at Dokkyo University School of Medicine. There were no differences in gastrointestinal manifestations or oral mucosal erosion in the survival and fatality groups, but signs of shock were only manifested in the fatality group. On admission, leukocyte count (WBCs) (16, 300±1, 360 vs 9, 500±2, 570/mm³, fatality vs survival group, p<0.05), serum amylase (510±100 vs 176±28Dye·U/dl, p<0.01), GOT (70±21 vs 24±3KU, p<0.05), and GPT (46±14 vs 19±4, p<0.01) were significantly higher in the fatality group. All patients in the survival group received primary treatment within 2 hours after drinking paraquat. The amount of paraquat ingested in the survival group was significantly lower, and their urinary paraquat concentrations were less than 30ppm. Thus, the amount of paraquat ingested and early elimination, within 2 hours, are important survival factors, and WBC count, amylase, and transaminase values are useful in making a prognosis.