Thyroid nodules are common and are often benign. The challenge has been to find the best method to identify and treat benign nodules. Fine-needle aspiration biopay is accurate, safe, and the most reliable method in nodule diagnosis. Fine-needle aspiration biopay has largely supplanted radioisotope scans and ultrasonographic imaging in nodule evaluation. Fine-needle aspiration has increased the frequency of carcinoma found among surgical specimens, from 15% to 45%, while decreasing by 25% the number of thyroidectomies performed for benign goiters. It is a cost-effective test that has decreased medical care costs by 20%. There are diagnostic pitfalls, but they should not cause major problems when the biopsy is performed by experienced personnel. Suspicious results usually are treated surgically, although thyroid peroxidase activity may help differentiate benign from malignant follicular adenomas. In experienced hands, complications are rare. Currently, we perform fine-needle aspiration as the initial screening test and base treatment on cytologic findings.