To evaluate the histologic alterations due to the fine-needle aspiration (FNA), a comparative study between 20 aspirated and 20 nonaspirated thyroidectomy specimens was performed. The nest common findings in the aspirated group were hemorrhage (80%) and vascular proliferation and/or vascular thrombosis (45%). In one of the aspirated cases with the cytologic diagnosis of follicular neoplasm, histologic sections revealed prominent vascular and endothelial proliferation. Fibrosis, cystic degeneration, and infarction were other histologic findings in the aspirated group. Hemorrhage was seen in 45% and cystic degeneration in 25% of the nonaspirated cases. Fifty percent of the nonaspirated cases did not have any additional findings.