Objective: Th e aim of this study was to investigate and compare the in vivo eff ects of prostaglandin E2 (PGE2) administered by different methods on orthodontic tooth movement and bone metabolism macroscopically, histopatologically, and biochemically. Methods: Forty-five young adult New Zealand rabbits were randomly divided into 3 experimental groups (n = 10/group), 1 positive control group (n = 10), and 1 negative control group (n = 5). The experimental rabbits were fi tted with springs exerting 20-g reciprocal force on the maxillary incisors and PGE2 (10 Ռg/mL) was administered by the intravenous, submucosal, or intra ligamentous route aft er appliance insertion and on days 1, 3, 7, and 14 thereaft er. All rabbits were sacrifi ced on day 21 and their premaxillae were resected for histologic evaluation. Results: Tooth movement was observed in the experimental and positive control groups, but the intraligamentous PGE2 group had the highest values of all analyzed parameters, including serum calcium and phosphorus levels and osteoclastic and osteoblastic populations (p < 0.001). Conclusions: Sub mucosal and intraligamentous PGE2 administration significantly increases orthodontic tooth movement and bone metabolism, but the intraligamentous route seems to be more eff ective. [Korean J Orthod 2012;42(3):118-128]