The subject of performing prophylactic or elective modified dissections of the neck in patients with clinically occult lymph nodal metastases from thyroid cancers is controversial since metastases to lymph nodes are associated with high rates of recurrences. Biopsies of sentinel lymph nodes can be performed successfully in patients with thyroid cancers since they can be identified with dyes or 99mTc. Our preliminary findings indicate that biopsies of sentinel lymph nodes can be useful in the treatment of thyroid cancers; however, the clinical significance of identifying metastases in regional lymph nodes by this technique remains to be determined.