Background: In developing countries like India, organophosphorus compounds (OPC) constitutes for 80% of pesticide poisoning. Creatine phosphokinase (CPK) is emerging recently as a prognostic marker in OPC poisnoning. This study is done to analyse the clinical utility of CPK in OPC poisoning patients. Aim: To estimate Serum CPK levels in patients who have consumed Organophosphorous compound (OPC) poisoning and to assess the role of Serum CPK (CPK) as a marker of severity and correlate it withthe incidence of respiratory failure and final outcome in OPC poisoning. Materials and Methods: 50 patients of acute OPC poisoning, aged 14 years and above, admitted in Rajah Muthiah medical college and hospital, within 6 hours of exposure irrespective of route of exposure and sex were selected and subjected for study. They were assessed clinically on admission by Peradeniya OPC Poisoning scales and categorized according to the severity. Then, they were also subjected to estimation of serum CPK at the time of admission and 48 hours after admission.Results: CPK values were increased among 60% of study group at 0 hours and 68% at 48 hours. There was a significant increase in serum CPK levels from 0 to 48 hours which is of high statistical significance (p =0.001). Conclusion:The correlations of serum CPK with outcomes such as ventilatory function and survival of the patient were statistically significant and positive at both periods of measurement. Therefore, serum CPK measurement is not only crucial at 0 hours, it is equally important to have serial monitoring of serum CPK levels, which ultimately tells the prognosis of the patients.