Weaning indices that are simple to derive and apply have been developed for predicting the likeliness of a patient to tolerate weaning. This study compared the Tobin Index and Integrative Weaning Index (IWI) to determine the better predictor for a successful weaning. This was a prospective observational study done on 60 patients on mechanical ventilation meeting the defined criteria whose physicians considered clinically stable to be given a weaning trial. Pre-determined threshold values of the Tobin index and IWI for determining a successful or unsuccessful weaning were used. A daily assessment was made with calculation of the Tobin index in GroupTI for extubation when Tobin Index≤105 breaths/min/L and IWI in GroupIWI when IWI>25 ml/min/cm H2O, with each group having 30 patients. A spontaneous breathing trial of 2 hours was given. The variables compared between the two groups were the outcome of weaning, duration of mechanical ventilation, ICU stay and hospital stay in days, and mortality. Comparison was done using Chi square test / Fisher’s exact test and Mann Whitney test. There was no significant comparison in terms of weaning success or failure, durations of mechanical ventilation, hospital stay and mortality. The duration of ICU stay was less and of statistical significance in the IWI group. However, the percentage of successful weanings while using the indices, both considered separately, was higher than the failures. Both the predictive indices studied did not successfully predict weaning outcomes in all the cases thus limiting their use in clinical practice. Key words: successful weaning, mechanical ventilation, weaning predictors, Tobin index, integrated weaning index