Objective: The aim of this study was to present a descriptive epidemiology of primary thyroid cancer in Tehran, Iran, using cancer registry data. Subjects and Methods: All cases of thyroid cancer registered from 1998 to 2001 in Tehran Metropolitan Area Population-Based Cancer Registry were used for this study. The incidence of thyroid cancer was estimated for the area covered by the cancer registry. Survival of patients was ascertained by telephone call to the patients or the patient's family and/or linkage of registry data to mortality data from the Bureau of Vital Statistics. Patient's survival was based on sex, age and morphological type of tumour. Results: Four hundred and twenty-nine cases of primary thyroid cancer were registered in the Tehran Metropolitan Area Cancer Registry. The incidence of thyroid cancer was 3.5 and 1.0 per 100,000 population per year for females and males, respectively. Seventy percent of tumours were papillary, 11% follicular, 6.2% medullary, and the rest were other subtypes. The papillary and follicular variants occurred in younger age: 43 ± 16 and 46 ± 13 years, respectively; the medullary and anaplastic variants occurred in older age: over 50 years. A 5-year survival rate was 82.2%, with median survival of 66 months and 95% confidence interval of 63 and 69 months. Men and women had a similar survival experience.Conclusions: While the incidence of thyroid cancer was slightly high, the descriptive epidemiology of thyroid cancer in Tehran did not manifest a unique feature. Tehran patients experienced a high rate of survival, and the survival time for males and females was similar.