Background: Intravenous bisphosphonate therapy is associated with preservation of femoral head sphericity and congruence in 77% of children with traumatic avascular necrosis. The aim was to describe the systemic effects of intravenous zoledronic acid (ZA) on bone and mineral metabolism in otherwise normal children and adolescents with femoral head AVN. Material and methods: 37 children (age 10.8+/-2.76 years) diagnosed with avascular necrosis AVN (Slipped Capital Femoral Epiphysis (SCFE), N=20 or Legg-Calve-Perthes disease (LCPD), N=17) were treated with at least 12 months of ZA. Bone mineral density (BMD) by DXA, bone morphometry and mineral homeostasis were evaluated at baseline, 6, 12 and 18 months. Data was retrieved retrospectively. Results: All children maintained height SD during treatment. BMI SD increased in the SCFE subgroup during the first 12 month period. Bone age increased appropriately. Age adjusted total body BMD, lumbar spine BMD and lean tissue mass adjusted bone mineral content (BMC) Z-scores increased significantly over the 18 months of treatment. The LS.BMD increase was greater in LCPD than in SCFE leading to more individuals with LCPD having a LS.BMD((age))Z-score over 2 SD at 12 months follow-up. Biochemical markers of bone turnover were decreased and PTH increased during the first 12 months of treatment and bone modeling was reduced. All markers stabilised over the next 6 months. There were no incidences of fracture, spondylolisthesis or osteonecrosis of the jaw. Conclusion: We here report that ZA in otherwise healthy children with femoral head AVN increases BMD - most pronounced in the LCPD group - and reduces bone modeling and turnover. Further efficacy and safety data are required before this therapy can be widely recommended.