This study deals with characterization and quantification of form I and form II of clopidogrel bisulphate (CLP), a selective and irreversible inhibitor of ADP-induced platelet aggregation. Thermal (DSC, TGA, HSM), crystallographic (XRD) and spectroscopic (FTIR) methods were used for characterization. After characterization of active pharmaceutical ingredient (API), these techniques were further used for identification of the polymorphic form present in three marketed formulations (tablets). FTIR method was successfully developed and validated for the quantification of form I in polymorph mixtures.