Several authors have noted a high incidence of thyroid carcinoma in patients with Hashimoto's thyroiditis (HT), and some have even considered HT a premalignant condition. The authors evaluated all patients with surgically proven HT at Beth Israel Medical Center in New York from 1985 through 1990. Of these 48 patients, 8 (17%) had thyroid carcinoma in addition to HT. No statistically significant difference between patients with and without concurrent carcinoma was noted in the percentage of patients with a dominant mass, irregular thyromegaly, compressive symptoms, suspicious fine needle aspiration biopsies (FNABs), or a cold nodule on thyroid scintigraphy. However, patients with neither a positive FNAB nor a cold nodule were much less likely to have carcinoma than patients with one or both of these tests positive (0% vs. 26%, P±.05). A management scheme for patients with HT is proposed to adequately and efficiently evaluate and treat patients for concurrent thyroid carcinoma.