BACKGROUND: A number of indices have been proposed as accurate predictors of weaning, but several studies have questioned the accuracy of these weaning indices in predicting the capability of independent breathing. The purpose of the study was to assess six standard bedside weaning indices and respiratory rate and tidal volume ratio (RRVT) of mechanically ventilated patients in the surgical intensive care unit (SICU). METHODS: The study was performed on 90 SICU patients who were mechanically ventilated. According to the outcome of weaning, they were divided into two groups, weaning success (n = 83) and weaning failure (n = 7). All subjects should have a PaO2 above 60 mmHg at an FiO2 of 0.4 and PEEP of 3 5 cmH2O and no PEEP in the extubated patients at the time of the weaning. Bedside weaning indices were respiratory rate (RR), tidal volume (VT), minute volume (VE), maximum inspiratory pressure (Pimax), vital capacity (VC), PaO2/FiO2 and RRVT. The predictive variables - sensitivity, specificity - of indices were calculated, and the data was also analysed with receiver-operating-characteristic (ROC) curves. RESULTS: Sensitivity was highest for VT (0.95), followed closely by the PaO2/FiO2 (0.94). Specificity was highest for Pimax (0.28). The VT was the best predictor of successful weaning, and Pimax was the best predictor of failure. The order of the area under the ROC curves was VC (0.761) followed by VE (0.636), VT (0.631), Pimax (0.546), PaO2/FiO2 (0.474), RR (0.457), and RRVT (0.339). CONCLUSIONS: Those weaning indices are good predictors of weaning success, but poor predictors of weaning failure. RRVT does not predict the weaning outcome.