Recently osteogenesis imperfecta has attracted much interest both of scientists and clinicians. Modern protein biochemistry and molecular biology have provided evidence that disturbed type I collagen synthesis is involved in the pathogenesis of the disease. Structural defects in the corresponding collagen genes have been identified in some cases, whereas others possibly are due to developmental defects leading to the persistence of a fetal state in collagen biosynthesis. A new clinicogenetic classification of the disease has brought a better understanding of the variable clinical course of the disease. Intramedullary telescopic rodding has proved to be a valuable orthopedic technique for the prevention and correction of fractures and deformities of long bones leading to successful rehabilitation of even severely affected patients.