Therapeutic measures aimed at boosting the immunity of HIV-infected patients are a critical component of strategies for effective therapy of HIV and AIDS. To improve immunocompetence in patients with progressive disease, autologous lymphocytes that were collected and cryopreserved earlier in the course of HIV-infection were reinfused. None of the 12 patients receiving cell infusions experienced any adverse effects. Improvements in immunologic parameters (CD4+ counts, CD8+ counts, or both; HIV-specific cytotoxic T-lymphocyte (CTL) activity; or viral load) were seen in seven patients. Restoration of the CD4+ count to the level recorded at the time of cell harvest was achieved in two patients with less advanced disease. Plasma HIV RNA was reduced by >0.5 logs in two of the four patients tested. These preliminary results suggest that cellular immunotherapy using cryopreserved autologous lymphocytes has the potential to improve some measures of immunity in patients with HIV/AIDS and warrants further investigation.