Abstract: The aim of this study was to clarify whether of Bone Marrow Myeloid tissue decreases the period of regeneration of tendon and enhances healing. Fifteen New Zealand white rabbits, with body weight ranging from 2.5 to 3 kg were used in this study, divided into three groups, five of each. The Achilles tendons were damaged by collagenase injection. Bone Marrow aspirated from the iliac crest and were injected to the injured tendon of the right leg and normal saline into the control leg. The animals were euthenized after 10, 20 and 30 days, respectively and tendon samples were taken for histopathologic examinations. Histopathologic observation demonstrated that Bone Marrow injections resolved edema, swelling and inflammatory cell infiltration in injured tendons. Also different degrees of increased fibroblast hypercellularity and vascularity were seen. In this experiment, the cellularity, vascularity, collagen density and collagen fibril organization were examined within and between the groups 10, 20 and 30 days after collagenase injection (p>0.05). The results showed no significant differences within the control and treatment groups and also between the control groups (p>0.05). However, significant differences were obvious between the treatment groups of 10, 20 and 30 days after collagenase injection (p<0.05). According to the results of the present study, injection of the bone marrow myeloid tissue may have effects on tendon healing in rabbit, as assessed by histopathological examination, compared to control group.