This study assessed the ability of the Sequential Organ Failure Assessment (SOFA) and Acute Physiology, Chronic Health Evaluation (APACHE) II scoring systems, as well as the Simplified Acute Physiology Score (SAPS) II method to predict group mortality in intensive care unit (ICU) patients who were poisoned with organophosphate. The medical records of 149 organophosphate poisoned patients admitted to the ICU from September 2006 to December 2012 were retrospectively examined. The SOFA, APACHE II, and SAPS II were calculated based on initial laboratory data in the Emergency Department, and during the first 24 hr of ICU admission. The probability of death was calculated for each patient based on the SOFA score, APACHE II score, and SAPS II equations. The ability to predict group mortality by the SOFA score, APACHE II score, and SAPS II method was assessed using two by two decision matrices and receiver operating characteristic (ROC) curve analysis. A total of 131 patients (mean age, 61 yr) were enrolled. The sensitivities, specificities, and accuracies were 86.2%, 82.4%, and 83.2% for the SOFA score, respectively; 65.5%, 68.6%, and 67.9% for the APACHE II scoring system, respectively; and 86.2%, 77.5%, and 79.4% for the SAPS II, respectively. The areas under the curve in the ROC curve analysis for the SOFA score, APACHE II scoring system, and SAPS II were 0.896, 0.716, and 0.852, respectively. In conclusion, the SOFA, APACHE II, and SAPS II have different capability to discriminate and estimate early in-hospital mortality of organophosphate poisoned patients. The SOFA score is more useful in predicting mortality, and easier and simpler than the APACHE II and SAPS II.