The purpose of this study is to formulate guidelines for proper surgical management of phyllodes tumor. It is a disease often misdiagnosed by pathologists and undertreated by surgeons. In a private surgical practice from 1956 to 1984, 16 patients were treated for phyllodes tumor. Findings from this retrospective review are compared with other reported series. Eleven benign cases survived 9 to 35 years. Four with malignancies developed metastases. One such patient, however, survives 11 years postmastectomy and two years after removal of a large thigh metastasis. An algorithm is presented for proper management of phyllodes tumor consisting of needle biopsy, tumor excision with testing for margins, and simple mastectomy for tumors > 5 cm and those of any size found to be malignant or borderline on permanent section or on the recommended secondary pathologic review. Surgical removal of a solitary distant metastasis should be considered for this resistant tumor.