Since 1984, a previously unrecognized respiratory coronavirus, causing a mostly unapparent infection, has rapidly and massively spread within the swine population in Europe, and few years later, a virus with similar characteristics has been identified in the USA. The agent, designated PRCV, appears to be derived from the porcine enteric coronavirus TGEV. The aim of the present article is to review comprehensively the state of the knowledge about this new virus and its infection. The review includes the following topics: epizootiology, molecular characterization and antigenic features of PRCV, pathogenesis and clinical aspects, immunity and laboratory diagnosis. The authors' views concerning the impact of the emergence of PRCV on both coronavirus research and swine production are presented in the conclusion.