This study uses the Severity Classification for AIDS Hospitalizations to examine and contrast the duration and costs of hospitalizations among 6,142 AIDS discharges from New York hospitals during 1985. Multivariate regression analyses of resource-use differences suggest that more severely ill AIDS patients have considerably longer stays and higher total charges, regardless of hospital type. Severity of illness alone accounts for most of the explained variation in hospital length of stay (LOS) and total charges. In contrast, other patient characteristics, such as gender, race, and reported drug use, are less important predictors of resource use. It was also found that public teaching hospitals serve somewhat more severely ill AIDS patients than those treated in private teaching hospitals. The study concludes that the AIDS severity classification facilitates interhospital comparisons of illness levels and variations in resource use.