['To identify prognostic factors in stage III and IV endometrial cancer with special attention to pretreatment platelet count.', '59 patients with FIGO stage III or IV disease operated on between 1983 and 1993 were analyzed. Patients with preoperative thrombocytosis were compared with those without thrombocytosis. Prognostic factors were analyzed with a Cox proportional hazard model.', 'With the exception of age, there were no significant differences between patients with or without thrombocytosis. At multivariate analysis, five-year disease-free survival was influenced significantly by FIGO stage (stage III vs stage IV; p = 0.009), thrombocytosis (p = 0.02) and cervical involvement (p = 0.024). Similarly, overall five-year survival was significantly influenced by stage (p < 0.001), cervical involvement (p = 0.005) and thrombocytosis (p = 0.01). Age, histology, grade, myometrial invasion, lymph-vascular space involvement or spread to adnexae were not significantly associated with survival.'] Is preoperative thrombocytosis an independent prognostic factor in stage III and IV endometrial cancer?