|Background. Thyroid cancer includes a broad spectrum of tumours with different prognoses. The global incidence has been increasing in recent years. Variables affecting its etiology are dietary, especially iodine intake and to a lesser extent selenium, environmental, like - ionizing radiation and, increased TSH level. These factors interplay with epigenetic and genetic changes within the cell. This review article presents thyroid cancer epidemiology, describes its main characteristics and the influence of environmental and lifestyle risk factors in the Czech Republic in comparison with other countries. Methods and Results. An epidemiological study of Czech patients with malignant thyroid carcinoma was made on the basis of the National Oncologic Registry (NOR) and Czech Statistical Office data summarized on the web portal SVOD. The data were compared with international data from the project GLOBOCAN 2008 Cancer Incidence and Mortality Worldwide. Apart from risk factors, prognostic factors with effect on patient survival were also analyzed. The survey showed that the incidence of thyroid cancer has been steadily growing in the Czech Republic. Since the beginning of the 1980s, it has increased 4 fold. It has a higher incidence than most other European countries but it is ranked with countries with an average and decreasing mortality. Obviously, the improved detection methods do not explain the growing incidence. The highest incidence is found for papillary carcinoma (PTC), now over 80% of cases. For follicular and medullar cancers, the incidence has not increased and for anaplastic carcinoma there is a slight decrease. Women over 40 years of age constitute the highest risk group. Conclusions. There are a number of reasons for these trends, such as improved diagnostic techniques using ultrasound and FNAB and more radical surgery. There are also dietary/environmental factors (iodine deficiency and to a lesser extent selenium), nitrates, polychlorinated biphenyls, increased ionizing radiation, and prolonged increase in TSH. The prognosis of patients with DTC depends on the age at the time of diagnosis. A favorable prognosis also depends on timely detection.