Retrospective review of patients treated with pamidronate from January 1995 to June 2006 in Sant Joan de Déu hospital (Spain). Patients:younger than 18 years that underwent treatment with the protocol for at least one year and with z-score < -2.5, fractures and z-score < -1 or documented bone pain with z-score < -1. They were classified into 4 groups: osteogenesis imperfecta, chronic treatment with steroids, disuse and other conditions. Interventions: single intravenous administration of pamidronate (30 mg in prepubescent patients and 60 mg in all other patients) every six months. Clinical, radiological data and bone mineral density were obtained basal and after each cycle. For each patient the ratio fractures/year during the treatment and the total increase in z-score (total ΔZ) after the treatment were calculated.