BACKGROUND: A study was undertaken to determine recurrence patterns and survival outcomes of stage I uterine papillary serous carcinoma (UPSC) patients. METHODS: A retrospective, multi-institutional study of stage I UPSC patients diagnosed from 1993 to 2006 was performed. Patients underwent comprehensive surgical staging; postoperative treatment included observation (OBS); radiotherapy alone (RT); or platinum/taxane-based chemotherapy (CT) ± RT. RESULTS: The authors identified 142 patients with a median follow-up of 37 months (range, 7-144 months). Thirty-three patients were observed, 20 received RT alone, and 89 received CT ± RT. Twenty-five recurrences (17.6%) were diagnosed, and 60% were extrapelvic. Chemotherapy-treated patients experienced significantly fewer recurrences than those treated without chemotherapy (P = .013). Specifically, CT ± RT patients had a lower risk of recurrence (11.2%) compared with patients who received RT alone (25%, P = .146) or OBS (30.3%, P = .016). This effect was most pronounced in stage IB/IC (P = .007). CT- and CT + RT-treated patients experienced similar recurrence. After multivariate analysis, treatment with chemotherapy was associated with a decreased risk of recurrence (P = .047). The majority of recurrences (88%) were not salvageable. Progression-free survival (PFS) and cause-specific survival (CSS) for chemotherapy-treated patients were more favorable than for those who did not receive chemotherapy (P = .013 and .081). Five-year PFS and CSS rates were 81.5% and 87.6% in CT ± RT, 64.1% and 59.5% in RT alone, and 64.7% and 70.2% for OBS. CONCLUSIONS: Stage I UPSC patients have significant risk for extrapelvic recurrence and poor survival. Recurrence and survival outcomes are improved in well-staged patients treated with platinum/taxane-based chemotherapy. This multi-institutional study is the largest to support systemic therapy for early stage UPSC patients. © 2009 American Cancer Society.