Bovine respiratory syncytial virus (BRSV) is a major cause of respiratory disease and a major contributor to the bovine respiratory disease (BRD) complex. BRSV infects the upper and lower respiratory tract and is shed in nasal secretions. The close relatedness of BRSV to human respiratory syncytial virus (HRSV) has allowed researchers to use BRSV and HRSV to elucidate the mechanisms by which these viruses induce disease. Attempted vaccine production using formalin-inactivated vaccine resulted in exacerbated disease when infants became exposed to HRSV. Cattle vaccinated with formalin-inactivated virus had enhanced disease when inoculated with BRSV. This article discusses various aspects of BRSV, its epidemiology, pathogenesis, diagnostic tests, immunity, and vaccination.