OBJECTIVE: To examine protective effects of Potentilla fulgens (P. fulgens) extract on cerebellar tissue damage of head-traumatized rats with respect to biochemical, histopathological, immunohistochemical, and ultrastructural analysis. STUDY DESIGN: Sprague-Dawley rats were subjected to traumatic head injury with a weight-drop device using 300 g-1 m weight-height impact. In our study the occipital lobe region was subjected to moderate trauma. Sixty-four rats were divided into 4 groups: group 1 (control group), group 2 (P. fulgens group [400 mg/kg/day i.p.]), group 3 (trauma group), and group 4 (trauma+P. fulgens [400 mg/kg/day i.p.]). Distilled water was used as vehicle. All rats were decapitated 5 days after the induction of trauma, and the protective effects of P. fulgens were evaluated by histological, immunohistochemical, and biochemical analyses. RESULTS: After trauma, degenerative changes and congestion were observed in Purkinje and glial cells. Elevated expression of E-cadherin in synaptic junctions, increased tumor necrosis factor alpha expression in Purkinje and glial cells, and elevated endothelin-1 expression in vessel endothelium were observed. Ultrastructural analysis showed loss of mitochondrial crista, and dilation of endoplasmic reticulum of Purkinje cells was observed. CONCLUSION: Although further studies are necessary to evaluate the time- and dose-dependent neuroprotective effects of P. fulgens, it may be a beneficial therapeutic agent for prevention of cerebellar damage following diffuse traumatic head injury. © Science Printers and Publishers, Inc.