Objective. To determine the efficacy of adjuvant platinum-based chemotherapy in Stage I uterine papillary serous carcinoma (UPSC). Methods. A retrospective multi-institutional investigation was performed to identify surgically staged patients with Stage I UPSC who were (1) treated after surgery with 3-6 courses of platinum-based chemotherapy without radiation from 1990-2003, and (2) followed for a minimum of 12 months, or until recurrence. Results. Six patients (IA-2, IB-3, IC-1) were treated with carboplatin (AUC 6) or cisplatin (50 mg/m2) alone. One patient recurred to the vagina, was treated with chemo-radiation, and is alive and well at 122 months. One patient recurred to the lung, liver, and brain, and died of disease at 24 months. The remaining 4 patients are alive with no evidence of disease 15-124 months (mean 62 months) after treatment. Two patients (IB-1, IC-1) were treated with cisplatin (50 mg/m2) and cyclophosphamide (1000 mg/m 2), and both are alive and well with no evidence of disease 75 and 168 months after treatment. Twenty-one patients (IA-5, IB-13, IC-3) were treated with a combination of carboplatin (AUC 6) and paclitaxel (135 mg/m 2-175 mg/m2). One patient recurred to the vagina after 3 cycles of carboplatin/paclitaxel, and was treated with chemo-radiation. She is now without evidence of disease 10 months after treatment. At present, all 21 patients with Stage I UPSC treated following surgical staging with carboplatin/paclitaxel chemotherapy are alive and well with no evidence of disease 10-138 months (mean 41 months) after treatment. Conclusion. Combination carboplatin/paclitaxel chemotherapy following surgery is effective in the treatment of Stage I UPSC. © 2005 Elsevier Inc. All rights reserved.