Introduction: Recent studies proved that Colchicine inhibits in-vitro proliferation of osteoblasts and osteosarcoma cells, and that Colchicine is non-selective mitosis inhibitor and selective inhibitor of mineralization. Aim: The aim of this study was to evaluate the effects of Colchicine (CO), given on a daily basis on healing process of bones. Materials and Methods: In a double blind prospective study, 3 groups of adult rats were checked. In each rat the left posterior tibia was broken. The study groups were treated with CO, one week before the fracture in one group, and on the fracture day in other group. The control group was not treated with CO at all. After six weeks the broken tibias were x-rayed and the radiographic union was compared between the groups. After the radiographic evaluation the bones were divided randomly to mechanical and histological evaluation. The union in each sample was estimated by 10 grades histopathological grading system. The mechanical tests were done, by checking the resistance to 3-points bending stress. Results: The results demonstrate signiþcant negative inßuence of chronic colchicine treatment on fracture healing. Radiographically, chronic treatment with colchicine reduced the union chance by 29. Clinically and mechanically, chronic treatment with colchicine reduced signiþcantly (p< 0.02) the callus strength. Pathological examination demonstrated mark reduction in the callus quality (p< 0.0001). Conclusions: In this study we proved that chronic treatment with colchicine reduce bone healing, and maybe the treatment policy (þxation methods, casting time, etc..) of skeletal injuries in colchicine treated patients, should be change.