OBJECTIVE This study aims to investigate the effect of pentoxifylline on fracture healing in an experimental animal model. METHODS Sixty-one male, Wistar-Albino rats were divided randomly into two groups as the pentoxifylline and control groups. Standard, closed femoral shaft fractures were established in all rats using a three-point bending device under general anesthesia. The rats were administered either pentoxifylline or isotonic NaCl injections everyday, beginning after production of fracture until they were sacrificed. Ten rats (11 rats in the pentoxifylline group on the 14(th) day) in each group were sacrificed on the 7(th), 14(th) and the 21(st) days and clinical, radiological, and histological examinations were performed to evaluate bony union. RESULTS Radiological evaluation of callus did not reveal any significant difference between the control and the pentoxifylline groups in the first, second and the third weeks. However histological callus formation was significantly superior in pentoxifylline group compared to the control group at the end of the first week and callus formation was better in the control group in the third week. CONCLUSIONS Pentoxifylline can be used to accelerate fracture union in early phases. Because of its hematological effects pentoxifylline accelerates the hematoma stage of fracture healing. But it inhibits fracture union in the later stages, presumably due to its anti-inflammatory effect. This should be taken into consideration during the clinical use of this drug.