Organophosphorous Insecticides (OPIs) have been profusely used and toxicity by them are common. Scoring systems are used as predictors of survival in severely ill patients. OPIs toxicity is associated with multiple biochemical abnormalities like changes in serum lactate. The aim of this study was evaluation the role of Acute physiology and chronic health evaluation II (APACHE II), Sequential Organ Failure Assessment (SOFA) scores, acetyl cholinesterase (AChE), and lactate enzymes in assessing severity, outcome and complications in acutely OPIs poisoned patients. This prospective cohort study was carried out on 36 OPIs poisoned patients admitted to Zagazig University Hospitals in seven months' period from the beginnings of May 2019 till the end of November 2019. The Peradeniya Organophosphorus Poisoning (POP), APACHE II and SOFA scores were calculated on the first day of admission. Serum lactate, and AChE enzymes were measured on admission and after 24 h. The cases were aged from 3 to 66 years old. As result of the study: APACHE II and SOFA scores were predictors of severity. The decrease in AChE level was correlated with the severity and complications but it was not predictor of them. Lactate was predictor of outcome and complications. Thus, APACHE II and SOFA scores can have used as predictors of severity. Also, lactate can be used as a predictor of outcome and complications.