An experience with approximately 6,300 fine needle aspirations of the thyroid was reviewed. The cytologic results were negative in 65% of the aspirates, suspicious for malignancy in 11%, positive for malignancy in 4% and nondiagnostic in 20%. Sensitivity in 382 cases of known malignancy was 98%, and the specificity of a positive cytologic report for malignancy was 99%. Repeat aspiration on initially nondiagnostic cases produced diagnostic results in more than half of the cases. The major limitation of the technique seems to be the lack of specificity in the group whose results are suspicious for malignancy, in large part due to an inability to separate cellular follicular or Hürthle-cell adenomas from follicular or Hürthle-cell carcinomas. The protocols for obtaining and processing the aspirates are briefly summarized.