Porcine reproductive and respiratory syndrome (PRRS) is caused by PRRS virus, which, like other members of the Arterividae family, has the ability to infect macrophages and to persist in tissues for at least several months after the acute stage of infection subsides. As a consequence, PRRS has a complex epidemiologic profile and has been especially difficult to control under the usual conditions of commercial swine production. Although vaccines are commonly used, vaccination is only one of several approaches to be considered in designing a control strategy. At least equally important are procedures developed on the basis of a thorough understanding of the epidemiology of the disease. The objective of this review is to summarize current knowledge in relation to PRRS virus (PRRSV) infection in the boar. The information available related to this topic will be summarized and discussed, and the implications for the control of the condition highlighted. The main emphasis will be on questions about the pathogenesis of infection, including duration of viremia and the origin of PRRSV found in semen; the clinical signs associated with the disease, paying special attention to the effects on seminal quality; the epidemiology of the condition, with special emphasis on the duration of PRRSV shedding in semen and the implications that this may have on venereal transmission, as well as the role that other potential routes of shedding may have on the dissemination of PRRSV.