The distal region of chromosome 5q contains a large number of genes, including those implicated in a variety of Mendelian disorders. One of these, Treacher Collins syndrome (TCOF1), is an autosomal dominant disorder of craniofacial development the features of which include conductive hearing loss and cleft palate. Previous studies have localized the TCOF1 locus between D5S519 (proximal) and SPARC (distal). To more accurately define the genetic distance between these markers, and to extend a high resolution genetic map of 5q31-33 to include additional highly informative markers, 15 loci (including polymorphisms for 4 known genes) were mapped through the Centre d'Etude du Polymorphisme Humain reference pedigrees. The resulting genetic map encompasses 29 cM on the sex-averaged map. To help integrate this linkage map with a physical map of the region, 13 loci from 5q31--33, including 6 genes, were used to construct a radiation hybrid map. As eight of the loci are common to both maps this has allowed us to combine the maps. The most likely location for the TCOF1 locus within this marker framework is in the D5S519-SPARC interval; a region estimated to be approximately 880 kb.