Objective: Early detection of uterine papillary serous (UPSC), clear cell (CCC), and grade 3 endometrioid carcinomas (G3EC) – all poor prognostic variants of endometrial carcinoma (EC) – is of particular clinical relevance. The study objective was to assess the utility of liquid-based cytology (Pap) in the detection of high-grade EC. Study Design: A retrospective, two-institution analysis of patients diagnosed with UPSC, CCC, or G3EC with a preoperative Pap from 1999 to 2010 was conducted. Results: One hundred and one patients were evaluated; 51.5% had UPSC, 27.7% had CCC, and 20.8% had G3EC. Stage I/II disease was found in 69.3% of patients, and 46/101 patients (45.5%) had abnormal Paps. Significantly more patients with UPSC had abnormal Paps (65.7%) than those with CCC (25%) or G3EC (23.8%; p < 0.001). An abnormal Pap was the only presenting clinical finding in a significant number of asymptomatic UPSC patients (26.9%) compared with 4% of patients with CCC and G3EC (p = 0.005). On multivariate analysis, UPSC histology was the only variable associated with an abnormal Pap. Conclusions: A high incidence of abnormal cervical cytology was observed in women with high-grade EC, particularly in UPSC patients. Although hypothesis generating, a proportion of asymptomatic UPSC patients had abnormal cytology, signifying that Pap smear screening may help detect the disease before the patient develops symptoms.