The analysis of 445 case records of patients operated for thyroid pathology is carried out. The data of pre- and introperative investigation and results of final histologic research of the removed tissue are compared. Traditionally used pre- and introperative methods of research (clinical, ultrasonic, FNAB, macroscopical estimation of thyroid tissue, a cytologic estimation of imprint smears) are not always reliable. The mistakes of pre- and introperative diagnosis have caused an inadequate surgery extent in 79 patients (17.9%) from 445. Search of new methods of diagnosis and differential diagnosis of the thyroid gland diseases is advisable.