The aim of this study was to analyze the clinicopathologic features and survival outcomes of women with synchronous primary carcinomas of the endometrium and ovary that were treated at Chiang Mai University Hospital between January 1995 and December 2004. During the study period, 43 women with such tumors were identified. These carcinomas accounted for 0.58% (95%CI=0.42-0.79%) of all gynecologic malignancies. Median age at diagnosis was 49 years (range: 34-60 years). Median body mass index (BMI) was 21.6 kg/m2(range: 15.5-27.7 kg/m(2)). The majority of women (65%) were premenopausal. The most common presenting symptom was abnormal uterine bleeding (42%), followed by a pelvic mass (30%). Twenty-seven (62.8%, 95%CI= 46.7-77.0%) women had concordant endometrioid carcinomas of the endometrium and ovary. Five (11.6%) women experienced tumor recurrence with median follow up 39 months (range: 1-85 months). The overall 5-year survival was 85.2%. There was no significant difference in survival outcomes among the women who had endometrioid/endometrioid histology and those who had other histological subtypes (P=0.674). In conclusion, synchronous primary carcinomas of the endometrium and ovary, although uncommon, should be considered in differential diagnosis in premenopausal women presenting with abnormal uterine bleeding and ovarian tumors. The prognosis of patients with these tumors appears excellent.