Kaposi's sarcoma-associated herpesvirus (KSHV) is the causative agent of two B cell lymphoproliferative diseases, namely primary effusion lymphoma (PEL) and multicentric Castleman's disease (MCD). KSHV infection of B cell lymphoma in vitro has been a long-standing battle in advancing human KSHV biology. In this study, a modified form of KSHV BAC36 named BAC36A significantly increased the fidelity of gene-targeted site-directed mutagenesis in the KSHV genome. This modification eliminates tedious screening steps required to obtain mutant clones when a KSHV BAC36 reverse genetic system is used. Coculturing B-cell lymphoma BJAB cells with KSHV BAC36A stably transfected 293T cells enabled us to infect BJAB cells with a KSHV virion derived from the KSHV BAC36A. The coculture system produced substantial amounts of KSHV infection to BJAB, meaning that KSHV virions were released from 293T cells and then infected neighboring BJAB cells. Owing to our success with the KSHV BAC36A and coculture system, we propose a new genetic system for the study of KSHV gene expression and regulation in B-cell lymphoma.