Case-control study comprised 100 histologically verified thyroid cancer patients (23 men, 77 women) and 100 hospital controls matched with cases by sex, age and place of residence. Various risk factors were studied to determine whether they were associated with the occurrence of thyroid cancer. According to the conditional logistic regression analysis, 6 were significantly related to the disease: Cigarette smoking (RR = 7.12 95% CI = 1.53-32.99), family history of any malignant tumors (RR = 5.84 95% CI = 1.76-19.44), history of goiter or thyroid nodules (RR = 27.69 95% CI = 3.11-246.14), long-term occupational exposure to chemicals (RR = 10.07 95% CI = 3.85-26.35), history of second primary tumors (RR = 15.49 95% CI = 3.46-69.30), and diagnostic X-rays exposure (RR = 7.56 95% CI = 2.85-20.07).