Outline of Protocol: There are one or more visits to evaluate the subject for their eligibility for an HIV vaccine trial. The evaluation will usually include laboratory studies, physical assessment, and counseling on avoidance of HIV infection, pregnancy and other HIV-related issues. Only those evaluations needed to determine eligibility for a particular study will be done. Evaluations of blood and urine samples other than those described in this protocol may be done if necessary for eligibility for a study.