We studied the impact of fine-needle aspiration biopsy on the management of patients with solitary thyroid nodules. Sixty-four patients were examined before the introduction of fine-needle aspiration biopsy, and 147 patients were examined after its introduction. The percentage of patients who underwent thyroid operation decreased from 67 percent to 43 percent, while the yield of carcinoma increased from 14 percent to 29 percent. Cost of medical care per patient declined by 25 percent. The results suggest that fine-needle aspiration biopsy provides valuable information to assist in the selection for surgery of patients with solitary nodules. Fine-needle aspiration appears to be safe, reliable, and cost-effective. The merits of the technique commend it for routine use in the evaluation of thyroid nodules.