Alterations of p53 suppressor gene as a possible indicator of the metastatic potential of thyroid carcinomas were evaluated in a cohort of 45 thyroid carcinomas. Well-differentiated papillary and follicular carcinomas were evaluated; the poorly differentiated and the undifferentiated forms were excluded from the studies. Tumors were divided into two groups: those giving no metastasis for >10 years and those developing metastasis within 5 years. Gene alterations were tested by immunocytochemical detection of p53 gene expression and by determining loss of heterozygosity (LOH). Considering the two methods together, p53 damages were observed in two out of 11 papillary carcinomas without metastasis (18.1%), one out of nine papillary carcinomas with metastasis (11.1%), two out of 14 follicular carcinomas without metastasis (14.2%), and five out of 11 follicular carcinomas with metastasis (45.4%). Statistical χ2test showed significantly (p = 0.05) only between follicular carcinomas with and without metastasis thus p53 damage may have an impact for metastatic potential of follicular thyroid carcinomas.