This supplemental issue of the Journal of Infectious Diseases is devoted to the important topic of primary human immunodeficiency virus type 1 (HIV-1) infection. It was prompted by the planning of the Acute HIV-1 Infection Meeting in Boston in September 2009, at which leading scientists and practitioners gathered to discuss new insights into the early, critical events of HIV-1 infection. The reviews that follow underline the current state of the field with regard to transmission biology of HIV-1; the clinical presentation, diagnosis, and management of primary HIV-1 infection; the pathogenesis of primary HIV-1 infection; and innate and adaptive immune responses to the virus. We trust that these findings have the potential to influence the development of effective vaccine strategies.