The goal of our study was to evaluate, and identify factors associated with, the adequacy rate of fine-needle aspiration (FNA) cytology of thyroid tumors to improve the quality of the procedure. We reviewed 1,611 cytological pathology reports of thyroid tumors of 871 patients between January 1998 and August 2008. The overall cytological adequacy rate was 53.9%. The freehand technique had significantly higher adequacy rates than the ultrasound (US)-guided technique (P < 0.001) regardless of size, tumor type, multinodularity, or location. Aspiration, performing specialist (endocrinologist versus radiologist), and size were the factors associated with adequacy rates. US-guided FNA is recommended in previous articles, but results in our clinic were in favor of freehand FNA. US guidance is a way to improve adequacy rates, but we would like to stress the importance of other factors like operator experience, education, and quality control in one's own institution before implementing techniques. Diagn. Cytopathol. 2012;40:E21–E26. © 2010 Wiley Periodicals, Inc.