The science of measuring bone mineral density has developed rapidly and, with it, an improved understanding of the efficacy and safety of various therapeutic interventions in adults. In contrast, the meaning and precision of such measurements in children are equivocal, and the concept of treatment for low bone density in the young patient is still largely undecided. In this report we review the present state of knowledge regarding the use of bisphosphonates during childhood to ameliorate the skeletal abnormalities associated with osteogenesis imperfecta, idiopathic juvenile osteoporosis, fibrous dysplasia of bone and cerebral palsy. Because of the paucity of long-term studies among children regarding the safety and efficacy of these drugs, it is difficult to formulate strong evidence-based recommendations for their use, except perhaps in children with osteogenesis imperfecta.