In this study some of the clinical and pathological aspects of thyroid carcinomas in Iran are defined. Until fairly recently, Iran was an area of endemic iodine deficiency. The medical records of 1177 confirmed cases of thyroid cancer treated over a 15-year period at 5 tertiary referral centers were reviewed. The female/male ratio was 1.8/1. Mean age was 42.8 +/- 0.9 years, male patients being significantly older. The most common clinical presentation (initial manifestation) was a central neck mass; 28.6% of the tumors had metastasized, usually to the cervical lymph nodes, by the time the patient presented with disease. The mean size of non-metastatic tumors was 5.0 cm at their longest diameter. The distribution of tumors in our study did not reflect the expectations for an iodine-deficient area, where follicular thyroid carcinoma is common, but rather what is seen in iodine-rich areas. Papillary and follicular types accounted for79.7% and 8.8% of cases, respectively.