To date, several hundred nonchimeric yeast artificial chromosomes (YACs) from the Centre d'Etude du Polymorphisme Humain containing polymorphic sequence-tagged sites have been mapped by fluoresence in situ hybridization (FISH) on human metaphase chromosomes. Because they carry an average of 1 Mb of human genomic DNA, CEPH YACs generate high-intensity in situ hybridization signals. The available set of cytogenetically and genetically anchored YACs, approximately one every 5-10 cM evenly spaced over almost the entire human genome, provides complex region-specific probes for molecular cytogenetics. YAC probes can be adapted with unlimited flexibility to specific FISH applications such as the study of chromosomal evolution. We have generated representational probes for YAC banding and painting of human chromosome 2 and its great ape homologs. Convergent inversions were found in the pericentric region of the gorilla and orangutan homologs of chromosome 2p.