295 Background: Liver toxicity limits radiation therapy for liver metastasis; however, robotic radiosurgery delivers effective doses with limited toxicities. Robotic radiosurgery may be an effective treatment for liver metastases in patients with lesions not amenable to surgical resection. Methods: We conducted a retrospective study of patients treated with robotic radiosurgery for liver metastasis at our institution from June 2008 and June 2010. Medical records were reviewed and all cases discussed in multi-disciplinary conference. Preradiosurgery and follow-up abdominal computed tomography (CT) scans reviewed for treatment response. Our primary endpoint was local recurrence, defined as increased enhancement or tumor progression within the treatment field on follow-up CT scan. Results: Thirty-three patients had 37 liver metastasis treated with robotic radiosurgery (17 colorectal, 4 ovarian, 4 breast, 3 melanoma, 2 liver, 2 lung, 1 gastric, 1 cholangiocarcinoma, 1 pancreas, 1 anal, 1 bladder). Eighteen of 33 patients (54.5%) had isolated liver metastasis. Prior to radiosurgery 27 of 33 patients (81.8%) had undergone surgical resection of primary tumor, 26 of 33 patients (78.8%) were treated with chemotherapy for metastatic disease, and 15 of 33 patients (45.5%) had non-liver radiation therapy. Median time from primary diagnosis to radiosurgery treatment was 33.3 months (5.7 to 320 months). Patients received median radiation dose of 30 Gy (22.5 to 42) over 3 to 5 fractions. Median follow up was 8.1 months (1.2 to 23.5). There were no cases of liver failure. Sixteen patients had disease progression outside the treatment field (15 liver, 6 systemic) with a median time to progression of 4.6 months (0.9 to 17.6). Five lesions (13.5%) had in field progression with a median time to progression of 10 months (2.6 to 13.1). Seventeen patients (51.5%) died during follow-up. Conclusions: Robotic radiosurgery offers a potential local therapy for patients with metastatic liver disease with limited toxicity. Longer follow-up and more patients are required to better assess its safety. Robotic radiosurgery may fill a role for patients with lesions not amenable to traditional ablative and surgical techniques.