All major community and academic clinics treating HIV-infected persons in the District of Columbia (DC) will initially be included in the development of a city-wide "DC Cohort" of HIV-infected persons in care, with consideration to be given subsequently to the inclusion of large private physician practices. Socio-demographics, risk factors, treatments, diagnoses, labs and procedures documented in outpatient medical record systems will be included in the DC Cohort database. Routine reports will be generated every six months for sites comparing their participants' socio-demographics, clinical status, treatments, and outcomes to all other data in the DC Cohort database, and other comparisons specifically requested by sites. All sites will be provided analytic support in research areas of interest.