Time dependent changes of parameters associated with malocclusion in patients with Duchenne muscular dystrophy (DMD) were examined in four dental developmental stages in 34 patients. We adopted activities of daily living (ADL) score, dental arch, craniofacial morphology, and electromyograms of the masseter and temporalis muscle as parameters. A comparison was made with the results in DMD subjects to data from healthy subjects with normal occlusion reported in the literature. In DMD subjects, manifestations of open-bite were related to ADL score, sagittal shortening and transverse expansion of the dental arch and vertical overgrowth of the lower jaw. Posterior cross-bite malocclusion was associated with differences in the time dependent changes between the jaws in transverse expansion. The malocclusion in DMD subjects was also related to the time dependent disproportional changes in masticatory muscle function by EMG. Occlusal deviation in DMD subjects became apparent at the late mixed dentition and malocclusion became definitely manifest from early permanent dentition.