To date, not many disorders have been associated with homeobox genes, especially with those belonging to the HOX family. This is particularly surprising, considering the body of evidence accumulated for a role of these genes in the control of mammalian development. Recently, this situation has changed and some congenital or somatic defects have been demonstrated to involve mutations in homeobox genes of the HOX, EMX, PAX, and MSX families, as well as in other novel genes containing either a paired- or bicoid-type homeobox.