OBJECTIVE: Among HIV-infected persons, we evaluated use of client partner notification (CPN) and health-department partner notification strategies to inform sex partners of possible HIV exposure, and prior exposure to partner counseling and referral services. METHODS: We conducted a cross-sectional, observational study of 590 persons diagnosed with HIV in the prior 6 months at 51 HIV test, medical, and research providers in Chicago and Los Angeles in 2003 and 2004. Logistic regression was used to identify independent correlates of using CPN to notify all locatable partners. RESULTS: Participants reported a total of 5091 sex partners in the 6 months preceding HIV diagnosis; 1253 (24.6%) partners were locatable and not known to be HIV-positive. Of 439 participants with ≥1 locatable partners, 332 (75.6%) reported notifying 696 (55.5%) partners by CPN (585, 84.1%), health-department partner notification (94, 13.5%), or other means (17, 2.4%); 208 (47.4%) used CPN to notify all locatable partners. Independent correlates of CPN included having fewer locatable partners and discussing the need to notify partners with an HIV medical-care provider (black and Hispanic participants only). Many participants reported that their HIV test or medical-care provider did not discuss the need to notify partners (48.8%, 33.7%, respectively) and did not offer health-department partner-notification services (60.8%, 52.8%). CONCLUSION: Many locatable sex partners who might benefit from being notified of potential HIV exposure are not notified. In accordance with national policies, HIV test and medical-care providers should routinely provide partner counseling and referral services to HIV-infected clients so that all locatable partners are notified and provided an opportunity to learn their HIV status.