Objectives. This study identified age-related differences in diagnosis and progression if HIV by analyzing a nationally representative sample of HIV-infected adults under care in the United States. Methods. We compared older (≥50 years) and younger participants stratified by race/ethnicity. Regression models controlled for demographic, therapeutic, and clinical factors. Results. Older non-Whites more often had HIV diagnosed when they were ill. Older and younger patients were clinically similar. At baseline, however, older non-Whites had fewer symptoms and were less likely to have AIDS, whereas at follow-up they had a trend toward lower survival. Conclusions. Later HIV diagnosis in non-Whites merits public health attention; clinical progression in this group requires further study.