Although individual bone dysplasias are rare, as a group they are relatively common and have a significant effect on morbidity and mortality at all ages. In this brief introduction, radiologic classification, diagnosis and differential diagnosis are given. The radiologic diagnosis is emphasized, since distinction among the various bone dysplasias is based largely on radiographic findings. Prenatal diagnosis relies heavily on high-resolution real-time ultrasonography of the fetus. Precise antenatal ultrasonographic diagnosis of a bone dysplasia may be very difficult; however, accurate differentiation of a lethal versus a nonlethal anomaly is relatively easy. There has been a recent explosion of knowledge about the genetic basis of skeletal dysplasias. Collagen gene mutations have been found to be responsible for osteogenesis imperfecta and many other bone dysplasias. The locations of the genes implicated in achondroplasia and some other chondrodysplasias are now known. Histologic analysis of the growth plate may also provide specific diagnostic features in achondroplasia and other bone dysplasias. A team approach is mandatory for the diagnosis and management of this fascinating and challenging group of diseases.