We examined the feasibility of sentinel lymph node biopsy for papillary thyroid cancer. In the dye injection method, 1% of isosulfan blue dye was injected around the tumor of 32 patients intra-operatively, and in the radioisotope (RI) colloid injection method, 99mTc-tin colloid was injected in 23 patients 1 day preoperatively. Lymph node mapping for detection of sentinel nodes was performed after thyroidectomy and central and modified lateral neck lymph node dissections. All dissected nodes were examined postoperatively by hematoxylineosin staining to determine whether or not metastasis was present. In the dye injection method, sentinel lymph nodes were identified in 30 (94%) of the 32 patients. Lymph node metastases were found in 14 patients, and some sentinel lymph nodes had papillary cancer metastasis in 13 patients. There was only 1 false-negative case. Sensitivity and accuracy of sentinel lymph node biopsy was 93% (13/14) and 97% (29/30). With the RI method, detection rate, sensitivity and accuracy of sentinel lymph node biopsy was 96% (22/23), 90% (9/10) and 95% (21/22), respectively. Our preliminary study indicated that sentinel lymph node biopsy was feasible in patients with thyroid cancer. It may be helpful in avoiding unnecessary lymph node dissection and improving quality of life in patients with thyroid cancer.