The study aims to evaluate the survival and prognosis of patients with malignant phyllodes tumor. Between 1982 and 1998, 37 women with malignant phyllodes tumor were treated at the Regional Cancer Center, Trivandrum. Twelve patients were recurrent. Survival was estimated using the Kaplan-Meier method. Patient, disease, and treatment factors were compared using log-rank test. The Cox-proportional hazard model was employed to identify the prognostic factors. Thirty-six patients had surgery. Twenty-five patients received postoperative radiotherapy, and 2 received chemotherapy in addition. The median follow-up was 43 months (range 1-170 months). Eight patients failed locally, and 7 of these were successfully salvaged by surgery. The 5-year overall survival was 74.2% (95% CI, 0.44 to 0.89), whereas 5-year disease-free survival was 59.6% (95% CI, 0.39 to 0.7). The margin of surgical excision was found to be the only independent prognostic factor (p=0.003). However, patients with tumor size more than 5 cm (hazard ratio 2.9) were found to have increased hazard, whereas those receiving adjuvant radiotherapy (hazard ratio 0.6), married women (hazard ratio 0.4), and those women over the age of 35 years (hazard ratio 0.7) showed a decreased hazards. Cystosarcoma phyllodes is a rare malignancy of the female breast. Surgery with adequate margins is the primary treatment. Adjuvant radiotherapy appears to improve the disease-free survival.