The evaluation and management of thyroid nodules is a common problem in medicine. In a review of 250 cases of thyroid disease seen at the 12 de Octubre Hospital (Madrid, Spain), 191 cases of solitary nodules and multinodular goiter were analyzed. The clinical findings, complementary studies, and postoperative histology were analyzed to determine the parameters most closely related to malignant thyroid processes. The overall rate of malignancy was 22.5%. Major clinical factors associated with malignancy were fixation to deep structures, cervical lymph node enlargement, and paralysis of the vocal cords. None of the complementary tests was absolutely reliable in excluding malignancy, but fine needle aspiration biopsy, in spite of its limitations, was the best diagnostic tool. Surgery is indicated if the benignity of a nodule cannot be confirmed.