Background: Traditionally, the follow-up of differentiated thyroid carcinoma consists of periodic withdrawal from L-T4-suppressive therapy to allow performance of a highly sensitive serum Tg measurement to detect recurrences. In this study, Lens culinaris agglutinin-reactive thyroglobulin ratios in serum were investigated to evaluate in usefulness for detection of thyroid carcinoma.Methods: The study was conducted on 93 serum sample from 23 healthy volunteers, 32 patients with benign thyroid tumor, 28 patients with thyroid carcinoma without 1 metastasis, and 10 patients with thyroid carcinoma with lymph node metastasis.Results: The Lens culinaris agglutinin-reactive thyroglobulin ratio in patients with thyroid carcinoma was found to be significantly lower than that in patients with benign thyroid tumor in case with serum thyroglobulin concentration > 200 ng/ml.Among cases of thyroid carcinoma with lymph node metastasis, Lens culinari agglutinin-reactive thyroglobulin ratios were significantly lower than in patient with thyroid carcinoma without metastasis and those with benign tumor regardless of serum thyroglobulin concentration.