Paget's disease is a localized mono- or polyostotic progressive bone disease of possibly viral etiology characterized by increased bone remodeling, leading to pain, fractures, and skeletal deformities with the risk of osseous, articular and neurological complications. Appropriate treatment should be given to any patient with symptoms and any patient with a pagetic lesion in a high risk location, even if the patient is asymptomatic. First choice of treatment are now potent new bisphosphonates of second generation. These substances are captured in pagetic bone at high concentrations giving a continuing therapeutic effect after application has ceased. Monitoring the course of biochemical markers of bone turnover allows individual decisions about duration and frequency of treatment courses.