This article will review current knowledge on CXCR in fish, that represent three distinct vertebrate groups: Agnatha (jawless fishes), Chondrichthyes (cartilaginous fishes) and Osteichthyes (bony fishes). With the sequencing of many fish genomes, information on CXCR in these species in particular has expanded considerably. In mammals, 6 CXCRs have been described, and their homologues will be initially reviewed before considering a number of atypical CXCRs and a discussion of CXCR evolution. [ABSTRACT FROM AUTHOR]