HIV-related symptomatology represents both an indirect measure of immune functioning and a clinically significant indicator of disease progression. The most widely used classification system for HIV-related symptomatology is the Center for Disease Control (CDC) system. Although the CDC scale has widely recognized clinical utility, it provides only nominal-level measurement, which may be problematic for both clinicians and researchers. This article describes the revision and validation of the HIV Center Medical Staging Scale (rHCMSS), and ordinal-level physical illness scale that provides a means of independently measuring the progression of HIV-disease symptomatology and immunological decline. Concurrent use of the rHCMSS, the CDC classification system, and T-lymphocyte and viral load data will provide a more comprehensive indication of HIV-disease progression for clinical and research purposes.