Acute HIV infection (AHI) is the earliest stage of HIV disease, when plasma HIV viremia, but not HIV antibodies, can be detected. Acute HIV infection often presents as a nonspecific viral syndrome. However, its diagnosis, which enables linkage to early medical care and limits further HIV transmission, is seldom made. We describe the experience of Yale's Center for Interdisciplinary Research on AIDS with AHI diagnosis in Connecticut, as a participating center in the National Institute of Mental Health Multisite AHI Study. We sought to identify AHI cases by clinical referrals and by screening for AHI at two substance abuse care facilities and an STD clinic. We identified one case by referral and one through screening of 590 persons. Screening for AHI is feasible and probably cost effective. Primary care providers should include AHI in the differential diagnosis when patients present with a nonspecific viral syndrome.