Two cases of follicular adenoma and a case of papillary carcinoma in three elderly females who had giant thyroid tumor with rapid growth within several months are presented. Intraglandular hemorrhage and necrosis of thyroid tumor were seen in two patients, one with follicular adenoma and one with papillary carcinoma. Cystic degeneration was seen in the patient with follicular adenoma. Massive hemorrhage, necrosis and cystic degeneration in the thyroid gland may be related to rapid growth of a thyroid tumor.