A boy 8 years and 7 months old who had contracted osteogenesis imperfecta was found to have dentinogenesis imperfecta of the primary and permanent teeth. Dentinogenesis imperfecta is a rare form of hereditary disease which causes local destruction to the dentine. There are two forms of dentinogenesis imperfecta, one which is caused solely by independent dystrophy of the dentine itself, and the other appearing with osteogenesis imperfecta. Osteogenesis imperfecta is thought to be a hereditary disease due to the deterioration of the osteoblast and the systematical disease of the mesenchymal tissue. Out of the three major symptoms for osteogenesis imperfecta, this case showed signs of fragile bones and blue scleras, but did not reveal signs of deafness. The characteristic structure of osteogenesis imperfecta of having a hyperbrachycepharic cranium was observed, as well as the underdevelopment of the jow and cross bite of _??__??__??_ was seen. The primary and permanent teeth which have already erupted, showed an opalescent color indicating the almost complete loss of the pulp cavity.<BR>Furthermore, the cervical region of these teeth showed a severe constriction and the roots were short.<BR>The pathohistological findings were obtained from extracted primary teeth. The enamel and mantle dentine was found to be of normal structure. But the region between the mantle dentine and the underlying dentine developed a layer of collagen fibers causing the enamel and the mantle dentine to shear from the circumpulpal dentine. Furthermore, the dentine showed laminations and an unorderly arrangement of the dentinal tubules. Several granule objects appeared including soft tissuelike structures in the dentine. According to the clinical, X-ray, and pathohistological findings, this case was classified as the Shields type I form of dentinogenesis imperfecta.