One of the major challenges in human B cell immunology field has been the objective to establish stable monoclonal cells lines that express the B cell receptor (BCR) on their cell surface and secrete antibodies. Such a system is extremely attractive not only for studying various aspect of BCR signaling but also for the generation of human monoclonal antibody and the analysis of the human B cell repertoire. This chapter describes an efficient method to immortalize and clone human B cells by Epstein-Barr Virus (EBV) transformation.