Aim: To determine the effectiveness of magnesium sulphate pretreatment on the onset of action of vecuronium and on the duration of action of vecuronium. 100 patients of aged between 18-55 years of ASA grade I and II undergoing surgery under Material And Methods: general anaesthesia were included and devided in two groups. Fifteen minutes before induction of anaesthesia, patients in Group- I received magnesium sulphate 40mg/kg in 0.9% normal saline 100 ml as an intravenous infusion over 15 minutes, and Group-II received 0.9% normal saline 100 ml without magnesium sulphate. After the end of surgery, when the amplitude of T1 was recovered to 10%, patients in both groups received inj. neostigmine 0.05 mg/kg and inj. glycopyrolate 0.02mg/kg IV. After neostigmin-glycopyrolate administration, T1 was measured up to 10 minutes in both groups. Neuromuscular transmission was assessed by electromyography on the left hypothenar muscle, using trans-cutaneous electrodes. The measurement was done after induction of anaesthesia. reduction in mean onse Result: t time was statistically highly signicant in magnesium sulphate group 171.26±30.97 sec vs control group 281.02 ± 33.22 second, (p<0.0001). The mean duration of action was prolonged in magnesium sulphate group 44.26±9.92min vs control group 28.6±6.83m ,and was statistically highly signicant, (p<0.0001). We used neuromuscular monitoring by train of four (TOF) because the response of neuromuscular blocking drugs is not predictable. Hence, TOF monitoring by NMT provided more predictable and rational approach to the use of muscle relaxants. Ma Conclusion: gnesium hastens the onset of neuromuscular blockade as well as reduces the variability of onset time of neuromuscular blockade and decreases the recovery rate of vecuronium and so prolonges the duration of action of blockade