The characteristics of pycnodysostosis, a new syndrome named in 1962, are reviewed in thirty-three cases taken from the literature. Pycnodysostosis is a genetic disease of bone characterized by short stature, skull dysplasia, flattened mandibular angle, dysplasia of the clavicles and terminal phalanges, increased bone density, and normal laboratory studies. Pycnodysostosis must be distinguished from cleidocranial dysostosis, osteopetrosis, progressive diaphyseal dysplasia, and idiopathic nonfamilial acro-osteolysis.