The inheritance of two restriction fragment length polymorphisms (RFLPs) on the short arm of the human X chromosome has been studied relative to Duchenne muscular dystrophy. This provides a partial genetic map of the short arm of the human X chromosome between Xp110 and Xp223. The data were derived from the segregation between a RFLP located at Xp21-Xp223, the DMD locus, and a RFLP located at Xp110-Xp113. The genetic distance from Xp110 to Xp223 was found to be approximately 40 centimorgans (cM). This provides experimental confirmation that 1cM corresponds to approximately 1,000 kilobase pairs of DNA for this region of the human X chromosome. Our data confirm that the DMD mutation lies between Xp223 and Xp110. The availability of flanking probes surrounding the DMD locus will assist in the ordering of further DNA sequences relative to the mutation.