Twenty percent of thyroid fine needle aspiration (FNA) is indeterminate. Because 3 in 4 of these are actually benign, a method of clarifying the pathology could help patients to avoid diagnostic thyroidectomy. Recently, core needle biopsy (CNB) has been proven to be highly reliable for this purpose. However, there are no reports of any potential cost benefit provided by CNB. Here we analyzed the impact on management costs of CNB compared with traditional diagnostic surgery in indeterminate FNA.