Alendronate should be considered as an alternative therapy of osteogenesis imperfecta (OI) because it significantly increased areal bone mineral density (BMD) and its Z score, decreased fracture incidence, inhibited bone resorption biomarkers. Alendronate exerted beneficial roles in different age brackets, especially in young patients with OI.

Inclusion Criteria:

1. children or adolescents aged 0-18 years,
2. had either a history of at least once minor-impact fracture or age and sex adjusted areal BMD Z score of -1.0 or less at lumbar spine or total hip;
3. with or without blue sclera, impaired hearing, joint hypermobility or dentinogenesis imperfecta;
4. with or without slim long bone; with or without cranial epactal bones, signs of multiple fractures, bony deformity in skeletal X-ray films.

Exclusion Criteria:

1. previous history of rickets, hyperparathyroidism, other metabolic or inherited bone diseases; malignant disease; coeliac disease; hyperthyroidism;
2. therapy history of BPs within recent two years; severe renal failure (creatinine clearance <40 ml/min), chronic liver disease; severe diseases of gastrointestinal tract;
3. unable to keep upright for at least 30 minutes daily .