Implementation of sensitivity analysis (SA) procedures is helpful in calibration of models and also for their transposition to different watersheds. The reported studies on SA of Soil and Water Assessment Tool (SWAT) model were mostly focused on identifying parameters for pruning or modifying during the calibration process. This paper presents a sensitivity and identi?ability analysis of model parameters that in?uence stream ?ow generation in SWAT. The analysis was focused on evaluating the sensitivity of the parameters in different climatic settings, temporal scales and ?ow regimes. The global sensitivity analysis (GSA) technique based on classical decomposition of variance, Sobol’, was employed in this study. The results of the study indicate that modeled stream ?ow show varying sensitivity to parameters in different climatic settings. The results also suggest that the identi?ability of a parameter for a given watershed is a major concern in calibrating the model for the speci?c watershed, as it might lead to equi?nality of parameters. The SWAT model parameters show varying sensitivity in different years of simulation suggesting the requirement for dynamic updation of parameters during the simulation. The sensitivity of parameters during various ?ow regimes (low, medium and high ?ow) is also found to be uneven, which suggests the signi?cance of a multi-criteria approach for the calibration of models. Copyright ? 2010 John Wiley & Sons, Ltd.