['To evaluate the influence of preoperative thrombocytosis on survival after surgery in patients with colorectal cancer (CRC).', 'Four hundred fifty-three patients who had undergone CRC surgery were retrospectively identified from institutional database. On the basis of receiver operating characteristic (ROC) curve analysis, they were classified into two groups: group A, with a preoperative platelet count of ≤300 (×10(9) /L), and Group B, with a preoperative platelet count of >300 (×10(9) /L). Uni- and multivariate analyses were performed to evaluate the relationship to overall survival. Kaplan-Meier analysis and log rank test were used to compare the survival curves between groups A and B.', 'There was a significant difference in overall survival between the two groups (P\u2009=\u20090.007). Multivariate analysis of selected preoperative clinicolaboratory characteristics showed that overall survival was associated with the platelet count (Group A/B) (odds ratio, 1.642; 95% CI, 1.025-2.629; P\u2009=\u20090.039) as well as the number of tumors (1/≥2), and the serum levels of C-reactive protein (CRP) and carcinoembryonic antigen (CEA).'] Is preoperative thrombocytosis associated with survival after surgery for colorectal cancer?