The objective of this study was to review the prevalence and prognostic impact of pretreatment thrombocytosis in patients with oral squamous cell carcinoma (OSCC). Medical records of 253 patients with OSCC were retrospectively reviewed. The relationship between the platelet count, TNM stage, histologic differentiation, recurrence rate, metastasis, and survival were analyzed. Pretreatment thrombocytosis was found in 61 (24.1%) of 253 patients and was associated with aggressive tumour growth (p=0.015), lymph node metastasis (p=0.009), and distant metastasis (p=0.001). Association with tumour recurrence fell just short of statistical significance (p=0.058). Patients with preoperative thrombocytosis had a poorer survival than those with normal platelet counts (p=0.004). Multivariate analysis using Cox's proportional hazards model indicated that thrombocytosis was an independent predictor of shorter survival (RR 2.48, 95% CI 1.30- 4.73, p=0.006).