A case-control study on thyroid cancer concerning 180 cases and 360 controls aged 20-70 years at diagnosis was performed. Both females and males were included. Of the cases, 63% had had papillary thyroid cancer. Work with diagnostic X-ray investigations constituted a risk factor for thyroid cancer of the papillary type yielding an odds ratio (OR) of 2.9 with 95% confidence interval (CI) = 1.1-8.3. For women only OR was 3.3 (CI = 1.2-9.8). The results also indicated that work as a lineman, which entails exposure to electromagnetic fields and chemicals, increased the risk. Exposure to impregnating agents gave an increased OR = 2.8 with CI = 1.0-8.6. For men only OR was 3.8 with CI = 1.1-16. Women who were previously smokers and female current smokers had significantly decreased risks with OR = 0.5 (CI = 0.2-0.96) and OR = 0.6 (CI = 0.3-0.96), respectively.