The purpose of this study is to describe the clinical findings, treatment, and outcome of patients with endometriosis-related cancers. Patients meeting Sampson and Scott's criteria for cancer associated with endometriosis in the Sacramento region were identified by chart review and pathology reports. Twenty-seven patients were identified with endometriosis-related malignancies (mean age 51.4 years). The site of origin was ovary in 17 (63.0%) and extra-ovarian in 10 (37%) including vagina, fallopian tube or mesosalpinx, pelvic sidewall, colon, and parametrium. The pattern of spread was local in five (18.5%), regional in 20 (74.1%) and distant in two (7.4%). Six patients had taken unopposed estrogen replacement (mean duration 23.4 years) and all six had extragonadal disease. Surgical procedures included hysterectomy, salpingo-oophorectomy, radical local excision, partial colectomy, and surgical staging. Eighteen patients received postoperative chemotherapy since the majority of patients had ovarian involvement. Fifteen patients received regional radiation therapy. Nineteen patients are without evidence of recurrence (70.4%, mean follow-up of 31 months). Endometriosis-related malignancies have a favorable prognosis. Extragonadal disease was commonly associated with unopposed estrogen replacement therapy. The predominance of local and regional disease strongly influence the application of treatment modalities.