Hematoma is a potentially life-threatening complication of thyroid surgery. Ketorolac is a nonsteroidal anti-inflammatory drug with known antiplatelet activity that is used for analgesia. The goal of this study was to determine the risk of hematoma in patients who received ketorolac in thyroid surgery. Retrospective cohort study. London Health Sciences Centre. A retrospective cohort study was conducted of patients who underwent thyroid surgery between 2002 and 2007. Data were analyzed using the Fisher exact test. Incidence of postoperative hematoma and perioperative ketorolac administration. Thirteen hematomas occurred in 799 patients. Of the 799, 183 patients received ketorolac (22.9%) and 616 did not. Five in the ketorolac group (2.73%) and eight in the nonketorolac group (1.30%) developed hematomas. The calculated relative risk was 2.10 (95% CI 0.70-6.35). Although there was an increased incidence of hematomas in the group receiving ketorolac, the difference was not statistically significant. The lack of significance may be due to the low number of hematomas.