Objective: This study aimed to clarify the efficacy of 2 therapies for patients with severe acuteorganophosphorus pesticide poisoning, including atropine adverse effects, the length of intensive care unit(ICU) stay, complications, and mortality.Methods: A retrospective cohort study of 152 cases collected from May 2008 to November 2012 at 2 urbanuniversity hospitals was conducted. Patients admitted to the hospital for organophosphate poisoning weredivided into 2 groups with different therapeutic regimens: group A was administered a repeated pulseintramuscular injection of pralidoxime chloride, and group B received the same initial dosage of atropine andpralidoxime chloride, but pralidoxime chloride intravenous therapy was administered for only 3 days,regardless of the length of atropine therapy. Subsequently, atropine adverse effects, length of ICU stay,complications, and mortality were statistically analyzed and compared between the 2 groups.Results: The total dose of atropine was 57.40 ± 15.14 mg in group Aand 308.26 ± 139.16 mg in group B; groupA received less atropine than didgroup B (P = .001). The length ofICU stay in group Awas reduced (P = .025),and group A hadfewer atropine adverse effects (P = .002). However, there was no significant difference in themortality or complication rate between the 2 groups (P N .05).Conclusion: In patients with severe poisoning, group A used less atropine, had fewer atropine adverse effects,and had a shorter ICU stay. We suggest that therapy should be started as early as possible using a sufficientamount of pralidoxime chloride started intramuscularly in combination with atropine and that the drugsshould not be prematurely discontinued.