Poisoning with organophosphorus (OP) compounds is/or may be a cause of morbidity and mortality across many countries including Egypt. The severity of OP toxicity should be assessed using scientific methods and clinical database which should be maintained so as to develop a uniform and effective management guideline. This study aimed to investigate the prognostic value of APACHE II score in predicting the severity and outcome of acute organophosphates poisoning and trying to set a cut off point for the score to help the management plan. A cross-sectional study was carried out on cases of acute OP poisoning admitted to the Poison Control Center (PCC), Ain Shams University Hospitals during the year 2010. They were divided into 2 main groups; Group I (GI): patients with acute OP poisoning not admitted to the ICU and group II (GII): patients with acute OP poisoning admitted to the ICU. Full history was taken from all patients or their relatives and they were generally examined on admission to obtain the data required for APACHE II score. This study included a total of 1553 OP poisoned cases. 1475 patients were not admitted to the ICU (GI) while 78 cases (5%) were admitted to the ICU (GII) who were subdivided into: GIIa (survivors) and GIIb (non-survivors) who included 18 cases (23%). The heart rate among cases admitted to the ICU was significantly lower (GII) than the non admitted cases (GI). The respiratory rate (RR) showed significant statistical difference between the two groups. The haematocrite value was elevated in GI and GII with significant difference between them. Cases admitted to the ICU showed a significant statistical difference regarding arterial blood gases (ABG) analysis compared to those not admitted. Serum Na+ and K+ were higher in the ICU group (GII) when compared with GI and the difference was statistically significant. On comparing group IIa (survivors) with group IIb (non-survivors), there were significant differences as regards age, mean arterial blood pressure (MAP) and serum K+. As regards APACHE II score results, a significant difference was found between GIIa and GIIb.  The best cut off value was > 8 and this proves the importance of APACHE II score in predicting the severity of acute orgnaophosphorus poisoning. It could be concluded that using APACHE II score facilitates the prediction of the severity and outcome of OP poisoned patients as it is simple, less time consuming and effective in emergency cases. Also, cut off point > 8 in APACHE II score may be used for ICU admission.