[en] Objective: To study the feasibility of target positioning in X-knife treatment on rat C6 gliomas and its acute therapeutic effects on the tumor. Methods: To established animal model C6 cells were inoculated into the right caudate nucleus for 20 Wistar rats by stereotactic procedure. On the 16th day after inoculation of C6 cells, tumor-bearing rats were treated with X-knife, 5 mm collimator and combination CT plain images with large field to the enhancement images of small field based on the latter was used to sketch the target position through the 3D workstation, 20 Gy in total. The acute therapeutic effect of X-knife treatment was evaluated with comparison to conditions of the rats in the tumor group. Results: There were 7 tumor-bearing rats in the treatment group, and two rats died at 1 hour and 3 days later; the remaining 5 rats were executed 5 days later. The overall conditions of 5 rats in the treatment group were much better than those in the tumor group (7 rats). Angiogenesis decresaing and hypocellular regions and tumor edema were observed more frequently in the treatment group that those in the tumor group (P<0.05). Conclusion: The method of target positioning with computerd tomography will play an improtant pole in further study on stereotactic radiosurgery of brain tumors in rats. (authors)