With the objective of creating standards for the volume of the thyroid gland by ultrasonography in the 0-16-year age group, thyroid volumes of 302 healthy children (150 boys, 152 girls) were measured by ultrasonography. The transverse (x), sagittal (y) and anteroposterior (z) lengths of the right and left lobes and isthmus were measured. Volumes of these were calculated by the ellipsoid volume formula [V = (pi/6) x x x y x z]. Statistical analysis was done using the Kruskal-Wallis and Student t tests. The cases were divided into six and eight groups by age and height, respectively. There was a significant positive corelation between thyroid volume, age, height and weight. Thyroid volumes in children of 12 years and over were significantly different from those in the younger age groups.