The utility of ultrasound volumetry of the thyroid is discussed on the basis of 414 different examinations. Analysis of the possible errors in calculations and the importance of the experience as well as practice are emphasized. According to the results of the cadaver studies, the difference between the in situ size and the size of the removed thyroid is explained by the changes of the blood, lymph and colloid flows after stasis. The preliminary data on the thyroid volume values in a randomized population pattern may serve as a model for a wide-ranging study aimed at the determination of the normal value in Hungary. Different volume values in the two phases of the menstruation period draw the attention to the effect of the female sex hormones on the thyroid volume, a factor that has to be considered in follow-up studies of female thyroid patients. Ultrasound volumetry is an indispensable method for the correct estimation of the thyroid volume changes in the course of suppressive treatment.