Background: Follicular carcinomas account for 15% of thyroid malignant tumors. The differential diagnosis between adenoma and minimally invasive follicular carcinoma is difficult and lacks reproducibility especially in frozen sections. As the diagnosis depends on finding foci of capsular invasion, multiple sections must be examined. Numerous immunohistochemical markers have been studied for determining malignancy. Aim: To assess the efficacy of HBME-1 and Cyclin-D1 as diagnostic markers for follicular thyroid carcinoma. Material and method: We evaluated retrospectively 21 thyroidectomy specimens of 18 women and 3 men with diagnosis of adenoma or follicular carcinomas, both by hematoxylin and eosin stain and by immunohistochemistry using the avidin biotin method for the markers HBME-1 and Cyclin D1. Results: The sensitivity and specificity of HBME-1 for the diagnosis of follicular thyroid carcinoma, were 88.9% and 100%, respectively whereas for Cyclin D1 the sensitivity and specificity were 22.2% and 100%, respectively. There were no false positive cases. Conclusions: HBME-1 has excellent sensitivity and specificity for the diagnosis of follicular carcinoma (Rev Méd Chile 2004; 132: 279-84).