Medical records for 79 cats with soft tissue sarcomas treated with preoperative or postoperative curative intent radiation therapy between August 1994 and February 2004 were reviewed. The purpose was to assess the effectiveness of preoperative and postoperative radiation therapy, and to determine the association of patient and radiation treatment variables with survival. Gender, age, weight, anatomic tumor site, packed cell volume (PCV), computerized vs. manual treatment planning, radiation field length, preoperative vs. postoperative irradiation, total radiation dose, and biologically effective dose (BED) were assessed as prognostic factors for survival. Fifty-six of 79 (71%) of cats were anemic within 2 weeks before or during radiation treatment. The median survival was 520 days for all cats, with a 1-year survival rate of 61.6%, and a 2-year survival rate of 41.6%. Only timing of radiation therapy relative to surgery and presence of a moderate or severe anemia were significantly related to survival. The median survival was 310 days for cats treated with preoperative radiation therapy, and 705 days for cats treated with postoperative radiation therapy (P=0.03). The median survival was 308 days for cats with a PCV<25%, and 760 days for cats with a PCV≥25% (P=0.017). Radiation therapy in combination with surgery results in relatively long-term survival in cats with soft tissue sarcomas. Anemia is common in cats undergoing radiation therapy for soft tissue sarcomas, and is associated with decreased survival.