Proper diagnosis and follow-up of children with testicular disorders depend on the presence of adequate references for testicular volume. The objective of this study was to determine the testicular volume by ultrasound in Turkish boys aged between 0 and 8 years. A total of 320 boys with bilaterally descended testes underwent scrotal ultrasound examinations. The testicular volume (mL) was calculated by the empirical formula of Lambert (V=L×T×AP×0.71) and the formula for an ellipsoid (V=L×T×AP×π/6). The testicular volume was compared with children's age, and Z-score data for weight, height, and BMI. The age-specific 3rd, 10th, 25th, 50th, 75th, 90th, and 97th percentiles of the testicular volume were produced and compared with the international references. The median (IQR) volume of the right and left testis were 0.75 (0.57-0.99) and 0.72 (0.56-0.98) mL (formula of Lambert), respectively; and 0.56 (0.42-0.73) and 0.53 (0.41-0.72) mL, (formula for an ellipsoid), respectively. The age-specific median of the average volume of the right and left testis estimated by the Lambert equation in the first five years was measured between 0.63 and 0.71mL, followed by an increase to about 1.31mL at the age of 8. This increase was highly statistically significant (p<0.0001). No significant association was found between the Z-scores for weight, height, and BMI of boys and the testicular volumes. This study provides the first national ultrasound-based estimates for testicular volume in Turkish boys aged 0-8 years.