The impairment of lymphocytes to proliferate to HIV antigen is a relatively early functional defect of cell-mediated immunity found in HIV-infected individuals. The finding of strong proliferative responses in nonprogressive HIV disease as well as its inverse association with viral load and clinical manifestation of AIDS supports the further use of this marker as a surrogate of disease progression. The observation that HIV-specific lymphocyte proliferation is associated with the production of CD8-derived HIV suppressive factors such as the beta-chemokines further supports this conclusion. These functional immune measurements provide an additional marker to monitor disease progression in HIV-infected individuals, along with the current standards of CD4 counts and viral load. Copyright 1997 S. Karger AG, Basel