Myotonic dystrophy is a multisystemic disease with varying symptomatology. The aim of this study was to compare the maximal bite force and handgrip force in patients with molecular diagnosis of myotonic dystrophy with those in a group of healthy individuals. It was hypothesized that these forces were reduced in the patients in comparison with the control subjects. The bite and handgrip forces of 37 patients with molecular diagnosis of myotonic dystrophy and 37 control subjects matched regarding age and gender were measured using an electronic dynamometer. The bite and handgrip forces were significantly lower in the myotonic dystrophy patient group when compared with the healthy controls (P < 0.0001). There were no significant force differences between genders, right- or left-hand side of mastication or hands in the myotonic dystrophy patient group whereas such differences were found among the controls. There were moderate but significant correlations between bite and handgrip force in both groups (r = 0.43-0.59; P < 0.01). It was concluded that there were considerable differences between the myotonic dystrophy group and the control subjects regarding both bite force and handgrip force. The weakness of the masticatory and hand muscles may have various negative consequences for oral function and dental health in patients with myotonic dystrophy.