The purpose of this study was to evaluate the results of interstitial radiosurgery (IR) with Photon Radiosurgery System (PRS) in 18 patients (P) with deep-seated brain primary or secondary tumors. Follow-up varied from 2 to 53 months (mean, 13.6 mo). Seven P with glioblastomas died due to tumor progression. Five P with metastases died for systemic disease while local control was achieved in all. Six P with low-grade astrocytomas were well and imaging showed tumor control. We conclude that PRS IR is effective in the treatment of metastases while it provides lower benefit in malignant gliomas. It could play a major role in low-grade astrocytomas.