Recently, a 15-fold increased risk of T cell lymphomas has been estimated in HIV-infected populations. This increase has been observed for all T cell lymphoma subtypes. In the present report we describe clinical and pathological features of three consecutive cases of peripheral T cell lymphoma (PTCL) with cytotoxic phenotype in HIV-positive patients that came to our attention in May-September 2002. The diagnosis of PTCL was made in lymph node (two cases) and in needle biopsies from liver and bone marrow of the same patient. The patients were two females (31 and 45 years old) and one male (49 years old). The risk factor for each patient was heterosexual, injecting drug user, and homosexual, respectively. CD4 cell counts were low (79-81 cells/mm3). Two patients were naive for antiretroviral therapy. At histological examination, all the involved tissues were effaced by a neoplastic proliferation of CD3+/CD8+ medium to large pleomorphic cells containing TIA-1+ cytotoxic granules and a few granzyme B+ granules. Neoplastic cells were not infected by EBV or by HHV-8. They were negative for the B cell antigens CD20 and CD79a, for CD30 and for CD56. Clonal T cell receptor-g (TCR-g) rearrangements were demonstrated in the three cases.