Human immunodeficiency virus type 1 (HIV-1)-infected patients (n = 335) in the US Air Force HIV Natural History Program were followed for 3 years (mean) after skin testing, immunophenotyping of CD4+ cell subsets, and measurement of in vitro interleukin-2 production after stimulation by phytohemagglutinin, alloantigens, tetanus toxoid, and influenza A virus. The T cell functional assay predicted survival time (P <.001) and time for progression to AIDS (P =.014). Skin testing for tetanus, mumps, and Candida antigen and the total number of positive tests (P <.001 for each) stratified patients for survival time. In a multivariable proportional hazards model, the T cell functional assay (P =.008), the absolute number of CD4+ T cells (P =.001), the percentage of CD4+CD29+ cells (P =.06), and the number of reactive skin tests (P <.001) predicted survival time. Thus, cellular immune functional tests have significant predictive value for survival time in HIV-1-infected patients independent of CD4+ cell count.