40 patients (24 adults and 16 children) with fibrous dysplasia (FD) were randomized to either receive alendronate administration in 6-month cycles for 24 months or placebo. The results revealed that in the alendronate group, NTX-telopeptides markers significantly declined at 18 months, however no significant difference in osteocalcin was observed between groups. Furthermore, areal bone mineral density in both normal lumbar bone and predetermined FD regions significantly increased in the alendronate group at 24 months, but not at 12 months. There was no significant difference in pain and function measures between groups.