Abstract: Histological and immunohistochemical studies of 29 cases of medullary thyroid carcinoma were presented.All tumors were classified as six histologic subgroups,i.e.nestlike,fascicular,carcinoid,trabecular,diffuse and glandular type.In 22 cases(75.9%),there was amyloid in the stroma(as determined by Congo Red Staining).The immunohistochemical results showed both keratin and calcitonin positive in 29 cases;26 chromogranin A positive;22 NSE positive;21 CEA positive and 29 thyroglobulin negative.Twenty-three cases were followed-up for 2.4 to 16.6 years.Statistically,the favourable prognoses were seen in female patients,patients lesser than 40 years old and patients with a high frequency(>50%) of calcitonin-immunoreactive tumor cells.