Forty-five surgically removed thyroid glands with well-differentiated carcinoma were histologically analyzed to clarify the relationships among vascular invasion, lymph node metastasis and extraglandular extension. Using Victoria blue-HE stain, vascular invasion can be detected as the evident finding of circular elastic fibers surrounding the cancer cluster. In our series, 60% of the subjects were positive for vascular invasion. Patients with vascular invasion tend to show lymph node metastasis and/or extraglandular extension. This correlation was statistically significant. Therefore, in a patient with lymph node metastasis and/or extraglandular extension, there is a greater possibility of vascular invasion being present as well.