The most serious complication associated with acute organophosphorus (OP) poisoning is intermediate syndrome (IMS) due to the possibility of developing respiratory failure. Abnormalities observed in repetitive nerve stimulation (RNS) may help to assess severity of IMS and eventually help to predict the cases which are more liable to develop respiratory failure. Also, some researchers suggested that IMS is associated with rhabdomyolysis which is followed by a rise in creatine phosphokinase (CPK) and lactate dehydrogenase (LDH) serum levels.  The aim of this work was to study the role of RNS and serum levels of CPK and LDH in predicting respiratory failure in acute OP poisoning. The study was carried out on 55 patients who were diagnosed as acute OP poisoning and admitted at Poison Control Center, Zagazig University Hospitals in the period from April 2013 to June 2014. The patients were subjected to estimation of serum pseudocholinesterase, CPK and LDH levels at time of admission and repeated at the 4^th day of poisoning.  Also, RNS test at 3 hertz (HZ) frequency was done to all patients at 2nd, 3rd and 4^th day of poisoning (the period at which IMS is expected). At the end of the study, it was found that the patients who developed respiratory failure showed significant increase in decrement response recorded by RNS and in serum CPK level. On the other hand, there was non-significant difference between patient who developed respiratory failure and those who didn't as regard serum LDH level. It was concluded from this study that, RNS test at 3 HZ and serum CPK level can be used as early predictors of respiratory failure in acute OP poisoning and it's recommended to use them especially in patients who are clinically diagnosed as severe poisoning at time of admission.