In the study authors tried to estimate the diagnostic value ofAgNOR number and MIB-1 and PCNA expression in thyreocytes from various pathological lesions, with special attention to differential diagnosis of border-line lesions (nodule in adenomatus goiter--adenoma--follicular carcinoma). Fifty four thyroid glands were examined (10 adenomatous goiters, 20 follicular adenomas, 10 follicular carcinomas, 14 papillary carcinomas). Statistical analysis of obtained results allows in most cases to differentiate carcinomas from benign nodular lesions. The best differentiating factor for border-line lesions (especially differentiation between benign nodular lesions, neoplasms, nodules in adenomatous goiter adenomas and adenomas carcinomas) has turned out to be MIB-1. PCNA expression has differed significant between adenomatous goiter and follicular carcinoma and between adenoma and both carcinomas. AgNOR number has only helped in differentiation between nodules in adenomatous goiter and follicular carcinoma - correlations for other lesions have not been statistically significant.