OBJECTIVE To study the relationships of Cyclin D1 expression with the posttraumatic intervals (PTI) following the cerebra, brainstem or cerebella contusion in human. METHODS 88 cases of brain contusions of the closed head injury were investigated with pathological and Cyclin D1 immunohistochemistry methods. The results were analyzed by image analysis technique (IAT). RESULTS The immunoreactivity of Cyclin D1 was almost disappeared in the core cells of the brain contusion. Cyclin D1-positive cells started to increase in the boundary of the brain contusion in the 1h group. Cyclin D1-positive cells were increased significantly in the 3 h-30 d groups and maintained at a high level in the boundary of the brain contusion of those groups. It is suggested that the Cyclin D1-positive cells were primarily origin from microglia and other glia. A few neurons expressed Cyclin D1. CONCLUSIONS Cyclin D1 can express in several kinds of brain cells following the contusion, especially in the glia cells. Cyclin D1-positive cells were increased obviously and rapidly after injury, so it could be used as a reference marker for early stage brain injury.