['To determine the impact of sex on disease-specific survival (DSS) in differentiated thyroid cancer.', 'Retrospective analysis of population database.', 'Adult patients with papillary thyroid carcinoma (PTC) or follicular thyroid carcinoma (FTC) were identified from the Surveillance, Epidemiology, and End Results Database between 1988 and 2003. Patients were grouped according to tumor type (PTC or FTC), with age, sex, tumor size, extension, and nodal or distant metastases recorded. The Kaplan-Meier method was used to compare DSS based on sex in each group.', 'We identified 36,725 patients, of which 77% were female and 23% were male. PTC represented 91.3% of patients and FTC the remaining 8.7%. Males with PTC and FTC were diagnosed at an older age and were significantly more likely to present with advanced-stage disease. In patients ≥45 years old, DSS was similar in male and female patients; however, in patients <45 years old, DSS was significantly worse in males. When compared by stage, DSS was similar among male and female patients with stage II PTC; however, males with stage I PTC had a minimally reduced DSS. Stage-stratified analysis revealed no DSS difference between male and female patients with FTC.'] Is sex an independent risk factor for survival in differentiated thyroid cancer?