This is a randomized trial to compare the effect of standard versus enhanced risk reduction counseling on risk behavior incidence in individuals receiving PEP medications. The study seeks to 1) determine if there are equivalent changes in the incidence of self-reported risk behaviors, STD incidence, and adherence to medications in individuals who receive enhanced risk reduction and adherence counseling and those who received standard risk reduction and adherence counseling; 2) evaluate viral and host biological factors involved in sexual transmission that may either influence PEP efficacy, or themselves be negatively or positively affected by the administration of PEP medications; and 3) contribute to the CDC registry in an attempt to provide crucial data for a case control analysis to establish the efficacy of PEP for sexual and injection drug use exposures. The principal outcome will be the change in participants' number of unprotected sexual acts following administration of PEP. This is defined as the number of prior 3-month acts of high risk unprotected sex, assessed at 12 months following a course of PEP, minus the number of unprotected acts the participant reported in the 3 and 6 months prior to beginning PEP (assessed at baseline). Methods to be used consist of interview data collection, questionnaires, risk reduction and adherence counseling and source recruitment counseling (index subject).