Form differences between biological structures can be evaluated using several approaches. When landmark data are available, a recently proposed method (euclidean-distance matrix analysis) seems to be able to differentiate between size and shape differences. This method also localizes those areas which differ most between the two structures. We have applied it to analyze the sexual dimorphism in dental arch form in a sample of 50 men and 45 women. Subjects ranged in age between 20 and 27 years, and had sound dentitions. Fourteen landmarks, corresponding to the centers of gravity (centroids) of the occlusal surfaces of all permanent teeth (right second molar to left second molar), were individualized on the dental casts of subjects. All the possible linear distances between pairs of teeth were computed, thus creating four mean form matrices (one for each arch within sex). Gender differences were tested by using euclidean-distance matrix analysis. No significant differences were demonstrated in the shape of arches, while male arches proved to be slightly bigger than female arches.