This supplement is consisted of 18 abstracts presented at the 14th North American colloquium on animal cytogenetics and gene mapping. The topics discussed include microsatellite DNA and sequence analysis of growth hormone receptor in cattle from the Chernobyl zone, characterization of chromosome aberrations in the horse, chromosome evolution in Perissodactyls, reciprocal translocation and sex reversal in cattle, comparative FISH mapping in domestic bovids, comparative genomics of vertebrates, cytogenetics and molecular analysis in purebred Spanish horses, genome analysis and its application in horses, genetic diversity of Zemaitukai horse, karyotypes of 3 Mexican species of Reithrodontomys, chromosome make-up of laboratory produced sheep embryos, and XX/XY chimaeras in a population of Arcott sheep. The relation between chromosome aberrations and some diseases and disorders (polydactylia, degenerative suspensory ligament desmitis, reproductive disorders) are given focus in several abstracts. The following topics are also given emphasis in some abstracts: high frequencies of chromosome abnormalities and SCEs in sheep herds exposed to high doses of dioxins; organization of bovine Y chromosome and male fertility genes; and X-linked gene expression in male and female in vitro fertilized and somatic cell nuclear transfer blastocysts.