The bromine addition to the SBR double bonds in chloroform at 0 degrees C has been investigated by FTIR, H-1 NMR and DSC techniques. In this case, bromine molecules react exclusively with the polydiene double bonds and the polystyrene units are unaffected. The bromine reacts preferentially with 1,4-trans double bonds of the polybutadiene segment of SBR. At low bromination level (below 15%) the bromine reacts mainly with the 1,4-trans double bonds of SBR, while at higher bromination level (up to 30%) the bromine shows the most reactivity toward the vinylic double bond. Above 30%, the addition reaction occurs on 1,4-trans double bonds. The microstructure of modified and unmodified styrene-butadiene copolymers were fully characterized by H-1 NMR technique. Expanded regions have been utilized to resolve the complex H-1 NMR spectrum and establish the compositional and configurational sequences of styrene-butadiene copolymers.