In a retrospective study of 100 patients operated on between 1974 and 1979 in our institution for thyroid cold nodules, an 8% incidence of thyroid cancer was found at surgery. Since 1979, F.N.A. was performed in 160 patients with thyroid cold nodules. Adequate cytological material was aspirated in 90% (144) of the cases; of those, a benign cytological lesion was diagnosed in 128 (89%) and suspicion of cancer in 16 (11%). To date fifty-one patients were operated: 41 with benign cytology and 10 with cancer suspicion; benignity was confirmed in 39/41 cases with benign cytology and malignity in 5/10 with suspect cytology. In conclusion, clinical diagnosis of thyroid cold nodules is greatly improved by the use of F.N.A. Despite the limitations of the technique, preoperative suspicion of cancer was increased 7-fold. Caution is recommended in the follow-up cases with benign cytology since, in these preliminary results, 2 false-negatives were found.