The major histocompatibility complex (MHC) region in fish has been subjected to piecemeal analysis centering on the in-depth characterization of single genes. The emphasis has been on those genes proven to be involved in the immune response such as the class I and class II antigen presenting genes and the complement genes. The Fugu genome data presents the opportunity to examine the short-range linkage of potentially all the human MHC orthologues and examine conserved synteny with the human and, to a more limited extent, zebrafish genomes. Analysis confirms the existence of a limited MHC locus in Fugu comprising the MHC class Ia genes and associated class II region genes involved in class I antigen presentation. Identification of additional human MHC orthologues indicates the completely dispersed nature of this region in fish, with a maximum of six MHC genes maintained within close proximity in any one contig. The majority of the other genes are present in the genome data as either singletons or pairs. Comparison with zebrafish substantiates previously observed linkages between class III region orthologues and hints at an ancient conserved class III region.