Using FISH and RH mapping a chromosomal map of rat chromosome 10 (RNO10) was constructed. Our mapping data were complemented by other published data and the final map was compared to maps of mouse and human chromosomes. RNO10 contained segments homologous to mouse chromosomes (MMU) 11, 16 and 17, with evolutionary breakpoints between the three segments situated in the proximal part of RNO10. Near one of these breakpoints (between MMU17 and 11) we found evidence for an inversion ancestral to the mouse that was not ancestral to the condition in the rat. Within each of the chromosome segments identified, the gene order appeared to be largely conserved. This conservation was particularly clear in the long MMU11-homologous segment. RNO10 also contained segments homologous to three human chromosomes (HSA5, 16, 17). However, within each segment of conserved synteny were signs of more extensive rearrangements. At least 13 different evolutionary breakpoints were indicated in the rat-human comparison. In contrast to what was found between rat and mouse, the rat-human evolutionary breaks were distributed along the entire length of RNO10.