Publisher Summary This chapter reviews all the factors associated with the Osteogenesis Imperfecta (OI) disorder. It is an inherited systemic disorder of connective tissue mainly expressed as “bone fragility,” resulting in fractures and skeletal deformity. It is classified into seven different clinical types differing in properties namely: (1) Type I OI, (2) Type II OI, (3) Type III OI, (4) Type IV OI, (5) Type V OI, (6) Type VI OI, and (7) Type VII OI. The clinical features, pathogenesis and differential diagnosis of OI in the newborn, children, and adults are described. Apart from the bone, there are involvements of other organs in OI: ocular involvement, hearing loss, cardiopulmonary involvement, neurologic involvement, hypercalciuria and renal calculi, and hyperplastic callus. The diagnostic procedures includes the bone biopsy, skin biopsy performed to determine fibroblast Type I collagen synthesis, and DNA analysis of collagen Type I Pro-1 and Pro-2 genes. The genetics, medical treatment and orthopedic treatments of Osteogenesis Imperfecta are also discussed.