ObjectiveDescription of the relationship between repeated measurements of CD4 lymphocyte count and development of AIDS in asymptomatic HIV-infected patients.DesignRepeated measurements of CD4 lymphocyte counts over an AIDS-free period in asymptomatic HIV-infected patients, and follow-up of the cohort to record subsequent clinical progression to AIDS.MethodsThe cohort was studied in a double-blind randomized clinical trial. CD4 lymphocyte counts were measured on three occasions over 8 months in 851 patients.ResultsEighty subsequent clinical progressions to AIDS were recorded during a median follow-up period of 15.3 months. Each of the three measurements of CD4 lymphocyte count were separately predictive of subsequent progression to AIDS. However, when the three measurements were included simultaneously in a predictive model only the last measurement showed a significant predictive value. Change in individual CD4 count was also related to the risk of developing AIDS, but was no longer significant when the most recent measurement was included in the model.ConclusionThese results indicate the closeness of the relationship between the actual state of the immune system and subsequent progression to AIDS.