Objective: To evaluate the therapeutic effects of radiosurgery on brain tumor using 99Tcm-MIBI brain single-photon emission computed tomography (SPECT). Methods : Fifteen normal volunteers and 49patients with brain tumor underwent 99Tcm-MIBI brain SPECT, and the tumor to non-tumor ratio (T/N)was calculated and compared before and after radiosurgery. The patients were regrouped according to different schedules for postoperative reexamination, and diagnostic sensitivity and specificity of 99Tcm-MIBI SPECT evaluated against that of conventional CT and magnetic resonance imaging. Results: After radiosurgery, the lesions were reduced or even disappeared in 22 cases, and tumor remnants or recurrence were found in 27 cases. The sensitivity, specificity and accuracy of 99Tcm-MIBI brain SPECT were 85.2%, 68. 2% and 77.6%,respectively. The sensitivity of postoperative 99Tcm-MIBI brain SPECT at 5.8 months was 92%, significantly higher than that at 3.1 months (89%, u=2. 2545, P＜0. 05), and its accuracy was also higher than those at3. 1 months (u=2. 5927, P＜0. 05) and at 9. 4 months (u=2. 1760, P＜0. 05). The preoperative T/N ratio averaged 9.5±7. 6, significantly lowered to 2.9±5.1 postoperatively (t=4. 4373, P＜0. 001). T/N ratio of recurrence group was remarkably higher than those of tumor remnants group (t=2. 1496, P＜0. 05), edema group (t= 9. 2186, P＜0. 001) and cicatrization group (t= 6. 3906, P＜0. 001). Conclusion: 99Tcm-MIBI brain SPECT is more accurate than CT in distinguishing tumor residuals from benign lesions such as edema and cicatrization. At about 6 months after radiosurgery, 99Tcm-MIBI SPECT can obtain optimal diagnostic effects.