Thrombocytosis has previously been shown to be an unfavorable prognostic factor in cervical cancer patients treated with irradiation. We evaluated the significance of thrombocytosis (platelet count > 400 x 10(9)/liter in 623 surgically treated patients with stage IB squamous cell carcinoma of the cervix. These patients had no gross evidence of extrauterine disease at the time of exploration, and none had metastasis to the para-aortic nodes. Fifty-nine (9.5%) of these 623 patients had thrombocytosis. The 5-year survival for patients with thrombocytosis was 82% compared to 83.5% for patients with normal platelet count (P = 0.4). Pelvic node metastasis was present in 13 (22%) of 59 patients with thrombocytosis, and 77 (13.7%) of 564 patients with normal platelet count (P = 0.1). There was a significant correlation between tumor size and platelet count. Patients with thrombocytosis had a mean tumor size of 27.9 mm, while it was 20.4 mm in patients without thrombocytosis (P = 0.002). Other factors found to be associated with thrombocytosis in this population were elevated white blood cell (WBC) count (P = 0.009) and history of chronic obstructive pulmonary disease (COPD) (P = 0.02). In a multivariate analysis for thrombocytosis adjusted for COPD, WBC count, and tumor size, tumor size continued to be statistically significant (P = 0.01). These data suggest that thrombocytosis is a marker of tumor burden and not an independent prognostic factor for progression-free interval or survival.