Organophosphorus compounds (OPC) are toxic substances that are responsible for the death of thousands of people annually. Objective: The Pattern of acute Organophosphorus poisoning (OPP) in patients admitted to Al-Dammam PCC (poison Control Centre) from 2009-2011. This study was subjected to cases admitted to AL-Dammam PCC, KSA due to OPP. The patients had been divided according to their age, into three groups: below 15 years, above 15 to 40 years, and above 40 years. According to severity, patients were divided into 4 groups. For all patients all of the following parameters were assessed on admission: Pseudo choline esterase (PChE),electrolytes, glucose, and white blood cell (WBC) count . Ninety five patients had been included within this study. The commonest nationality was Saudi (n=45, 47.3%). The commonest route of poisoning was ingestion (57, 6%). The female: male ratio was: 1:2.17. The majority of cases occurred in the summer. The mean age in suicidal (n=17) cases were 22.8±18.1years with Pseudo choline esterase (PChE) level: 95.59±32.13 UKat/L, while in accidental cases (n=78) mean age was 45.8±16.7 with PChE level: 493.61±31.2. Mean PChE levels in severe cases were: 37.95±15.94 U Kat/L with age 42.3±17.7 and 437.25 ±323.92 U Kat/L in mild cases with age 41.7±16.7 years. Most of cases admitted to EMD ward n= 40(42.1%). There was a statistically negative significant correlation between the duration of hospital stay, with PChE levels on admission, (r = - 0.396), and with age (r = - 0.209). There was a strong positive relationship (P