Because AIDS is such a relatively recent disease and AIDS treatment modalities are changing so quickly, little is known about how to measure quality of care for AIDS patients. Initial RAND research has found that AIDS impatient mortality rates differ as a function of hospital experience with patients with AIDS. This study will be a five-year retrospective evaluation of quality of care, outcome, and resource use. Specifically, we propose to build on earlier research by studying how mortality and other outcome measures for AIDS patients hospitalized with their first episode of Pneumocystis carinii pneumonia (PCP) are affected by patient, hospital, physician and city characteristics. The two-year study will extend the use of both medical record reviews and Uniform Hospital Discharge Data Sets (UHDDS) to examine the effects of process of care, severity of illness, comorbidity and risk group on mortality and resource use. This study will also allow us to validate a sample methodology to assess quality of care for AIDS patients. We will examine AIDS care in 5 high-AIDS-familiarity and 10 low-AIDS-familiarity hospitals located in each of four large and geographically diverse metropolitan areas--Los Angeles, Chicago, Miami, and New York. Sixteen-hundred patient records will be reviewed. The study utilizes the expertise of a number of RAND AIDS researchers as well as program coordinators/consultants in the four study sites who are leaders in AIDS research. It will be the first large-scale analysis of variations in care for AIDS patients that addresses differences in risk group, type of hospital, city, and severity of illness.