This study evaluated the predictive validity of two clinical staging systems for HIV infection (the Rabeneck and Royce systems) using data obtained from the Department of Veterans Affairs Cooperative Study Number 298, a randomized clinical trial involving 335 symptomatic patients with CD4 counts of 200 to 500/mm3. The relation between the HIV clinical stages and progression to AIDS was examined using Kaplan-Meier estimates, and Cox models were used to determine if the stages remained predictive after controlling for CD4 count. Both systems were significant independent predictors of progression to AIDS. This work demonstrates that simple, valid staging systems for HIV infection can be developed that provide greater prognostic distinction than the CD4 count alone.