Background: The Group B Streptococcus (GBS) is the major etiologic agent of neonatal sepsis and meningitis around the world. Our laboratory isolated a Chilean GBS bacterial strain from a newborn with septicemia (NCBI code KU736792). We cloned the Surface Immunogenicity Protein (SIP) gene and expressed it in E. coli cells. The SIP is present in all GBS serotypes and could be a good target for vaccine and detection methods. Aim: Purify and perform partial biochemistry characterization of SIP. Methods: The DNA of the SIP gene was sequenced and the SIP purification was carried out by low and high-pressure Liquid Chromatography (LPLC and HPLC). Purified SIP was analysed by SDS-PAGE, Western blot, MALDI-TOF MS and Size Exclusion Chromatography (SEC) by HPLC. Results: The SIP gene was sequenced and submitted to NCBI with the KX363665.1 code. The SIP was purified by low-pressure affinity, his-tag chromatography and the molecular weight was estimated as 53 kDa. The MALDI-TOF MS analysis corroborated the protein’s identity. The SIP was analysed by SEC and we observed a homodimer, but in presence of 6M urea, it was dissociated to a monomer. Conclusion: We purified the SIP isolated from a Chilean GBS bacterial strain. The preliminary experimental observation indicates that the protein was expressed like a homodimer and that the real molecular weight is lower than reported to date. The biologic function of this protein is not yet understood and a study of the secondary protein structure is under development.