The expression of P53 and P21WAF1 proteins was analyzed immunohistochemically in archival material derived from 12 cases of follicular thyroid carcinoma, 57 cases of follicular adenoma and 17 cases of nodular goiter. In the follicular carcinoma group 6 out of 12 cases (50%) were positive for P53 protein and 4 out of 12 cases (33.3%) were positive for P21WAF1 protein. In the follicular adenoma group, 18 out of 57 cases (31.6%) were positive for P53 and 16 out of 57 cases (28.1%) were positive for P21WAF1 protein. No positive cases of P53 or P21WAF1 proteins presence were found in the nodular goiter group. Positive correlation between the expression of P53 and P21WAF1 proteins was found for follicular carcinoma and adenoma groups (p = 0.034 and p = 0.002, respectively). The obtained results demonstrate that simultaneous immunohistochemical detection of P53 and P21WAF1 proteins expression may be useful in determining functional status of P53 protein, helping to interpret expression of P53 protein in thyroid follicular carcinoma cells.