No study has been published to date in Spain about the value of the American Thyroid Association (ATA) ultrasound risk assessment of thyroid nodules applied by endocrinologists. To assess the diagnostic performance of ATA thyroid nodule risk classification applied by endocrinologists with respect to histological results. A retrospective, observational study of 317 patients (mean age, 51.7±13.7 years; 83.3% women) with thyroid nodules (maximum diameter: 3.2±1.4cm) who underwent US-guided FNA in endocrinology between October 2015 and December 2018, were classified based on the ATA ultrasound risk assessment. Surgery was performed in all of them. Quality criteria of the ultrasound classification were assessed as compared to histological results. Overall, 61.2% of nodules assessed were classified as benign (n=3) and very low (n=60) or low suspicion (n=131), 11.7% as intermediate suspicion (n=37), and 27.1% as high suspicion (n=86). Benign nodular disease was found in 260 patients, and thyroid cancer in 57 patients. There were 14 incidental papillary microcarcinomas. Classification of thyroid nodules as high suspicion showed a high diagnostic performance to identify malignant nodules (87.7% sensitivity, 86.2% specificity, negative predictive value 97.0%), improving sensitivity (93.0%) and reducing specificity (73.1%) when considering high and intermediate suspicion nodules as a risk for thyroid cancer. Application by endocrinologists of the ATA ultrasound risk assessment of thyroid nodules shows a high diagnostic performance to identify malignant thyroid nodules before surgery. Copyright © 2019 SEEN y SED. Publicado por Elsevier España, S.L.U. All rights reserved.