Virion-associated Vpr induces activation of caspases 3/7, 8, and 9 in human activated PBMCs. Activated human PBMCs from donors 1 (A to C) and 2 (D to F) were mock infected or infected with Vpr(+)trans or Vpr(−) viruses with equivalent numbers of infectious units. Caspase 3/7 (A and D), 8 (B and E), and 9 (C and F) activities were measured for each sample at 8.5 (T 8.5), 24 (T24), 32 (T32), and 48 (T48) h postinfection. Uninfected cells treated with 2.5 μg/ml of the Fas CH11 antibody or 1 μM of staurosporine (STS) for 2 to 6 h were used as positive controls for the assay at each time point. The results are shown as means plus standard deviations.