The aim of this study was to assess the long-term efficacy and safety of i.v. neridronate in the treatment of osteogenesis imperfecta (OI). One hundred and fourteen patients affected by OI were included in the study. Neridronate was administered by i.v. infusion at the dosage of 2 mg/kg, up to a maximum of 100 mg at three-month intervals for 3 years. Dual X-ray absorptiometry of the lumbar spine, hip, and ultradistal and proximal radius were evaluated every 6 months. Blood calcium, phosphate, albumin, fasting urinary calcium/creatinine ratio, total serum alkaline phosphatase, and bone alkaline phosphatase were obtained at baseline and every 3 months. The mean lumbar spine and total hip BMD significantly increased from baseline to any time point (p