To determine the standard testicular volume growth, 1985 males aged 0 to 28 years were subjected to measurement by means of Hynie's testometer and the results were related to the body size (testicular volume cm3/Livi index). Data for comparison were obtained from a gypsy and a non-gypsy sample. While at the ages of 0 to 9 years the volume did not show any notable variation, there was a conspicuous and rapid (approx. 10-fold) increase between 10 and 15 years. The maximum size was attained among the non-gypsies at 17-18, among the gypsies at 21-22 years. The average volume for every age group above 19-20 years was higher in the gypsy than in the non-gypsy sample. In each group, from the start of puberty the right testis was bigger on the average than the left.