Abstract: Objective: To analyze the results of surgery on different types of medullary thyroid carcinoma (MTC) and to explore the optimal surgical manipulation of primary foci. Methods: We retrospectively reviewed data from 91 patients with MTC who were treated with surgery in Tianjin Cancer Institute and Hospital from 1992 to 2005. Germline RET proto-oncogene mutation analysis was performed in family members of patients with hereditary MTC. Results: Of the 91 cases of MTC, there were 10 cases of hereditary MTC (6 cases with bilateral tumors and 4 cases with unilateral tumors). Of the 4 cases with unilateral tumors, 3 cases had tumor recurrence in the contralateral gland during follow-up. Bilateral MTC occurred in 90.0% of patients with hereditary MTC. Bilateral tumors were found in 11 of 81 sporadic MTC patients. The other 70 patients with sporadic MTC had unilateral tumors. During follow-up, 4 in 70 cases had tumor recurrence in the contralateral gland. Bilateral MTC occurred in 18.5% of patients with sporadic MTC. Of those relatives of patients with hereditary MTC who were screened, 3 were identified with the RET proto-oncogene mutation. Conclusion: Family members of patients with hereditary MTC should be genetically screened. Total thyroidectomy should be performed in hereditary MTC patients and in sporadic MTC patients with bilateral tumors. For sporadic MTC without evidence of bilateral tumors, lobectomy with isthmectomy is the appropriate treatment.