The Duchenne muscular dystrophy locus is remarkable in that it shows a high mutation rate and the majority of mutations found are deletions. These deletions are generated as meiotic as well as mitotic events and occur preferentially in the central region of the gene. Nothing is known so far about the mechanisms involved. This paper reports the first sequencing of deletion junctions in the dystrophin gene. The data from a study of two patients with deletions in the central region of dystrophin show the breakpoints to lie in regions of introns in which stretches of dA-dT are seen. The relationship between these observations and possible mechanisms for the mutations is discussed.