Primary effusion lymphomas (PEL) form a subset of AIDS-related lymphomas and usually have a poor prognosis. Although Kaposi's sarcoma-associated herpes virus (KSHV) is often associated with PEL, very little is known about the exact mechanisms or causative effects of these associations. We investigated the chromosomal imbalances in six KSHV-positive PEL cell lines using comparative genomic hybridization analysis. We defined the shortest regions of overlaps for genomic gains on six chromosomes: 1q31, 4q31 approximately q33, 7q10 approximately q21, 8q21.1, 12q0 approximately q23, and Xp11 approximately q21. The recurrent nature of the gains found in these chromosomal regions suggests that these imbalances play roles in the pathogenesis of PEL.