Scintagraphic patterns of cold thyroid nodules taken by the scintillation camera with radioactive iodine-131 were reported. Previous reports published by others on this subject were based on the scintillation scanner which gave us less sharp resolution than the scintillation camera. Our data indicate that the defect pattern is largely dependent upon the existence of the capsule as well as the size of the nodule. In general, a benign nodule shows defect having a rather smooth margin with somewhat distended normal thyroid tissue, whereas malignant one, if it has no capsule, shows an irregular or straight margin. However, the defect pattern of malignant nodule covered with a capsule is similar to that of benign nodule. A defect of the entire unilateral lobe and highly irregular-shaped defect spread over bilateral lobes are suggestive of malignancy. These findings seem to be generally similar to those reported by others. However, pull-up phenomenon of lower pole coexisting with the defect in the upper half is highly suggestive of malignancy, especially of papillary type. As long as defect (negative) pattern is investigated, the diagnosis of cold nodule inevitably meets certain limitations. To avoid this problem, the radiopharmaceutical which exclusively concnetrates in malignant nodule should be searched. Then, the scintigraphic diagnosis of thyroid nodule will become more reliable.