Five polymorphic CA-dinucleotide repeats, identified in cosmids from the short arm of the human X chromosome, have been characterized and localized to Xp21.1 (DXS572), Xp11.4 (DXS556, DXS574), and Xp11.22-p11.23 (DXS722, DXS573). Genetic mapping with respect to five reference markers that include the gene for CGD (CYBB in Xp21.1), complemented by physical mapping information, has indicated the order tel - DXS572 - CYBB - DXS1110 - DXS556 - DXS574 - DXS7-DXS426-DXS722-DXS573-DXS255-cen.