Surgical staging of endometrial carcinoma includes the collection of peritoneal washings in the abdomen and pelvis. A positive finding upstages patients to International Federation of Gynecology and Obstetrics stage IIIA. However, the prognostic significance of such an upstaging, and thus the justification for the routine performance of this procedure, is unclear. This 5-year retrospective study was conducted to determine the frequency and prognostic significance of upstaging of endometrial carcinoma based solely on positive washings. The cohort for the study was collected by review of pathology reports of all washings that were performed prior to hysterectomies for suspected endometrial carcinomas over a 5-year period (01/1995-12/1999). Cases with positive cytology were selected if there was no grossly apparent intraperitoneal disease, no histologic evidence of extra-uterine tumor and the cases would otherwise have been considered stage I or II (case group). An age-matched control group was selected of stage I and II patients with the same histologic subtypes and negative washings (n=19). Of 220 endometrial carcinomas, peritoneal washing cytology was abnormal in 19 (8.6%) and was solely responsible for upstaging only 10 patients (4.5% of all cases, eight-endometrioid, one-serous, one-mixed; nine stage IA or IB and one stage IIB). Adjuvant therapy was administered in 90% of the case group and 74% of the control group. After a median follow-up of 51 months (case group) and 63 months (control group), we found only a single patient with progression of disease (recurrence, metastases or death) in the control group. It is concluded that abnormal cytology without other evidence of extrauterine disease leads to upstaging of a minority of endometrial carcinoma patients (4.5%), but does not appear to affect their overall outcome. Although this is a small single site study, it raises questions about the value of this procedure in patients with endometrial cancer.