The deciduous and permanent teeth in some patients with osteogenesis imperfecta syndromes are blue or brown and opalescent. As shown by radiologic examination, the pulp chambers and root canals are completely or partially obliterated by abnormal dentin. The junctions between the crowns and roots are more constricted than normal. Deciduous opalescent teeth lose their enamel readily and wear more easily than normal. Unusual wear does not occur as frequently in permanent opalescent teeth as in deciduous teeth. No relationship has been shown between the number of fractures or deformity and the degree to which the teeth are affected. In contrast, other patients with osteogenesis imperfecta have normal teeth. These clinical differences in the dentitions support the concept of genetic heterogeneity is osteogenesis imperfecta and provide information useful in genetic counseling. The differential diagnosis of opalescent teeth in osteogenesis imperfecta is not difficult provided that detailed clinical and radiologic examinations of the dentition are performed. Patients with osteogenesis imperfecta and opalescent teeth should be evaluated as soon as the deciduous teeth erupt, so that an attempt can be made to prevent loss of tooth structure. However, methods of dental care in osteogenesis imperfecta are not well delineated and deserve further study.