“Brittle bone” disorder or Osteogenesis Imperfecta (OI) is a heritable disease of the connective tissue, primarily characterized by multiple fractures of bone due to minor trauma. OI manifests most strongly during childhood, with the incidence of fracture tending to decrease when the skeleton reaches maturity. OI is estimated to affect 1 in 10,000 to 60,000 people in the United States; however, this estimate may be inaccurate due to misdiagnosis and unreported cases of milder forms of the disease. Although relatively rare, 01 is the most common hereditary bone disease, and most OI patients can be characterized as “osteoporotic” since they do not develop normal bone mass at any age. Currently there is no cure for OI, but bisphosphonates, a class of drugs that axe used in osteoporosis management, decrease the incidence of fracture, increase mobility, and decrease pain associated with the disease. The mechanism of action of bisphosphonates is not entirely understood, however, and studies such as this one seek to understand the effects of these drugs on the bone tissue and structure. To examine the effect of pamidronate treatm ent on OI bone, heterozygous B6C 3Fe — a/a — Colla2oim/+ hybrid breeder mouse pairs were obtained from Jackson Labs (Bar Harbor, ME). At four weeks of age the mice pups were assigned to one of three intraperitoneal pamidronate doses: a control (Omg/kg/mo), a low (5mg/kg/mo), or a high (10mg/kg/mo). At 12 weeks the mice were sacrificed via carbon monoxide asphyxiation The femurs and tibias were excised and used to characterize the cross-sectional geometry, failure properties (3-point bending), and dynamic mechanical properties. The fracture surfaces of wildtype and oim/oim mice femurs were also characterized in an attem pt to quantitatively, using the fractal dimension, compare the mode of fracture in these animals. Our data show that pamidronate treatm ent decreases the overall length but increases the diameter and the cortical thickness of the bone. We further show that treatm ent increases the structural stiffness of the bones but does not affect the material properties or yielding characteristics. Our study is to our knowledge the first to examine the dynamic mechanical properties and the fractal nature of OI bone