Total 19 cases of medullary thyroid carcinoma (MTC) diagnosed at Chang Gung Memorial Hospital from Jan. 1979 to Dec. 1994 were studied retrospectively. All of them were pathologically proved. All cases except one were thought as sporadic MTC. The gender distribution showed a female preference with female : male (F:M) ratio of 3.8:1. The mean age at diagnosis was 44.9 +/- 13.7 years. The most common clinical presentation was thyroid mass in all (100%). The staging of MTC in our cases demonstrated: 12 (63%) stage I, 1 (5%) stage II, 3 (16%) stage III, and 3 (16%) stage IV. Thyroid ultrasonography with fine-needle aspiration cytology (FNAC) were performed in 15 patients. Eleven cases were diagnosed as malignancy, including 5 cases diagnosed as MTC preoperatively. Neck nodal metastases were noted in 7 cases and all occurred in tumors larger than 3 cm. All cases received operation according to clinical stage. Six of 7 patients who had preoperative calcitonin data showed abnormal high values. After operation, there were 8 patients with persistent hypercalcitoninemia. Of these, 5 received 131I therapy which induced undetectable calcitonin level in 2 stage I patients. Three cases received external beam radiotherapy but all failed. During a period of 0.5 to 9.4 years follow-up (mean +/- SE: 3.6 +/- 0.7 years), 3 patients died of pulmonary infection, 1 lost follow-up and 15 patients are alive and well. In conclusion, the preliminary data suggests that the medullary thyroid carcinoma in Taiwan has following characteristics: (1) gender distribution showed a female preference; (2) accuracy of preoperative FNAC was 42%; (3) most of the diagnoses of MTC were made postoperatively.