The use of dipeptidyl aminopeptidase IV (DPP IV) staining by azo-coupling in preoperative and intraoperative diagnostics of thyroid lesions is presented. In a series of 200 histologically confirmed cases examined, the sensitivity and the specificity were 71% and 99%, respectively in 124 smears, and 70% and 94%, respectively in 189 frozen sections. DPP IV expression showed high negative predictive value as well. DPP IV is suggested as an additional tool in the preoperative and intraoperative diagnostics of thyroid lesions.