OBJECTIVE: Thyroid cancer is the most common endocrine malignancy and the fifth most common malignant neoplasm of the female sex. During the past several decades, an increasing incidence of thyroid cancer has been reported. The mortality from thyroid cancer is comparatively low and remains almost stable showing a slight increase. It is currently unclear whether the observed increase in thyroid cancer is real or is due to overdiagnosis, as clinical and pathology findings may be sometimes doubtful in diagnosing the incidence and mortality of thyroid cancer. The cancer has different distribution depending on gender, race, age and environmental conditions. Despite considerable progress in the understanding of the biology and molecular pathways of carcinogenesis in the thyroid gland, less progress has been made in terms of defining a risk profile for thyroid cancer. The only risk factor which is systematically documented as carcinogenic for thyroid is exposure to ionizing radiation during childhood. Recently several studies are examining as risk factors diet and exercise, benign thyroid diseases as well as a genetic factors that influence the incidence and mortality of the disease. To the best of our knowledge there are only few epidemiological studies examining the effects of exposure to chemical agents on thyroid cancer's "behavior".CONCLUSION: The effect of risk factors for the onset and progression of malignant thyroid tumors constitutes a field that requires further study in order to provide answers on the pathogenesis of the disease, so as to take preventing measures and finally manage to decrease thyroid cancer incidence and mortality.