Chromosome deletions leading to the hemizygous loss of groups of contiguous genes are a major cause of human congenital defects. In some syndromes haploinsufficiency of a single gene causes the majority of the syndromal features, whereas other diseases are thought to be the consequences of a combined haploinsufficiency. In the case of the DiGeorge and velocardiofacial syndromes, caused by deletions within 22q11, the genetic analyses have so far failed to implicate a single gene. By virtue of FISH analysis and the creation of a BAC/P1 genomic clone contig we have mapped 19 murine homologues of genes and nine EST groups from the region deleted in DiGeorge syndrome and found them to be linked on mouse chromosome 16. Rearrangements during the divergence of mouse and human have led to differing gene orders in the two species, with implications for the most appropriate means of mimicking particular human deletions. The map confirms and extends previous analyses and the contig resources toward the generation of targeted deletions in the mouse.