We have previously shown that expression of HIV-1 vpr in yeast results in cell growth arrest and structural defects, and identified a C-terminal domain of Vpr as being responsible for these effects in yeast. In this report we show that recombinant Vpr and C-terminal peptides of Vpr containing the conserved sequence HFRIGCRHSRIG caused permeabilization of CD4+ T lymphocytes, a dramatic reduction of mitochondrial membrane potential and finally cell death. Vpr and Vpr peptides containing the conserved sequence rapidly penetrated cells, co-localized with the DNA, and caused increased granularity and formation of dense apoptotic bodies. The above results suggest that Vpr treated cells undergo apoptosis and this was confirmed by demonstration of DNA fragmentation by the highly sensitive TUNEL assay. Our results, together with the demonstration of extracellular Vpr in HIV infected individuals, suggest the possibility that extracellular Vpr could contribute to the apoptotic death and depletion of bystander cells in lymphoid tissues during HIV infection.