The significance of peritoneal washing cytology in the management of patients with gynecologic cancer is well established. Its microscopic evaluation, however, is not always straightforward. Previous studies have identified some of the conditions that may result in misinterpretation of cytologic results. This report reviews the literature and describes other sources of diagnostic difficulties and clues for correct diagnosis. In addition, an outline for distinguishing endosalpingiosis from borderline and well-differentiated serous carcinoma is proposed.