Nineteen adult patients with progressive HIV1 infection, which progressed within 5 years from acute HIV syndrome to final AIDS were studied. Changes in HIV antibody titer, viral RNA load, peripheral T lymphocytes and subpopulations as well as CD4/CD8 cell ratio and cell death (apoptosis) were monitored. The data were collected for comparison with HHV-6 infection, which involves the same cell populations yet patients usually recover, and to serve as a further basis for future computer simulation studies. The results showed progressive increases of viral RNA copies in the patients' plasma even during clinical latency, which correlates with lymphocyte apoptosis and CD4 cell loss. Besides apparent direct CD4 cell destruction, there was indication of a disturbed intrathymic T cell differentiation. Pathologic cell changes in HIV infection continue until final death of the patient and do not return to normal after variable times as in HHV-6 infection. While HHV-6 infection can serve as models for immunostimulation, with or without immune dysregulation in computer simulation studies, HIV infection is a model for immunostimulation with final immune deficiency and cellular aplasia.