CDC has revised the classification system for HIV infection to emphasize the clinical importance of the CD4+ T-lymphocyte count in the categorization of HIV-related clinical conditions. This classification system replaces the system published by CDC in 1986 (1) and is primarily intended for use in public health practice. Consistent with the 1993 revised classification system, CDC has also expanded the AIDS surveillance case definition to include all HIV-infected persons who have < 200 CD4+ T-lymphocytes/microL, or a CD4+ T-lymphocyte percentage of total lymphocytes of < 14. This expansion includes the addition of three clinical conditions--pulmonary tuberculosis, recurrent pneumonia, and invasive cervical cancer--and retains the 23 clinical conditions in the AIDS surveillance case definition published in 1987 (2); it is to be used by all states for AIDS case reporting effective January 1, 1993.