Objective Our aim was to determine the outcomes of Stage I uterine papillary serous carcinoma (UPSC) patients with and without adjuvant therapy after comprehensive surgical staging. Methods Patients with FIGO Stage I UPSC diagnosed from 1987 to 2000 were identified from tumor registry databases at four institutions. A retrospective chart review identified 60 women who underwent comprehensive surgical staging, including a total hysterectomy, bilateral salpingo-oophorectomy, pelvic/para-aortic lymphadenectomy, and peritoneal cytology. Fisher's exact, χ2, and log-rank tests were used for the statistical analyses. Results Of the 60 Stage I patients, 40 (66%) patients received no adjuvant therapy, 12 (20%) received adjuvant radiation therapy (XRT), 7 (12%) received adjuvant chemotherapy (CHM), and 1 (2%) received both XRT and CHM. There were seven recurrences in the observation group versus two recurrences in the XRT group (17% vs 16%, P = 0.9). No recurrences or deaths were observed in the CHM group. The mean disease-free survival rates for the observation and the XRT groups were 31 and 41 months, respectively. The mean overall survival rates for the observation and XRT groups were 39 and 40 months, respectively. The 5-year disease-free survival rates for the observation and XRT groups were 65 and 60%, respectively; the 5-year overall survival rates for observation and XRT groups were 66 and 59%. There was no statistical difference in overall survival among the three groups. Conclusions In this largest reported series of surgical Stage I UPSC patients, recurrence rates were lower than those published in previous studies, suggesting a potential benefit of comprehensive surgical staging in these patients. The risk of recurrence and the mean overall survival were similar between surgical Stage I UPSC patients who were managed conservatively and those treated with adjuvant radiation therapy. These data question the benefit of radiation therapy in UPSC patients with disease confined to the uterus. Finally, given the absence of recurrences and disease-related deaths for adjuvant chemotherapy in these patients, a Phase II/III trial evaluating adjuvant chemotherapy in surgical Stage I UPSC patients should be considered. © 2003 Elsevier Inc. All rights reserved.