Occlusal conditions and skeletal facial morphology in patients with amelogenesis imperfecta were studied in order to reveal a supposed relationship between skeletal morphology and a high prevalence of open bite. Records and dental casts were available for 26 cases, and lateral cephalograms in 19 of these. An open bite was present in 11 patients of both sexes, but was more frequent in males than in females. It occurred in cases with enamel defects of hypomineralisation type as well as in those with hypoplasia.15 linear and 10 angular measurements from the cephalograms were compared with those of matched controls. Both males and females with enamel defects were found to have significant skeletal features, characteristic of the so-called open bite skeletal deformity. The skeletal deviation was more marked in males than in females. The pattern of an open bite skeletal deformity, although less marked, was also present in patients with the enamel defect but without an open bite occlusion. The open bite occlusion frequently found in cases of amelogenesis imperfecta is therefore considered to be of skeletal origin, although the causal relationship between the enamel defect and the skeletal deformity remains to be explored.