Among the techniques available to assess bone quality, quantitative ultrasonography of the proximal phalanges of the hand (QUS) has emerged as particularly attractive. In this study, amplitude-dependent speed of sound (AD-SoS) and bone transmission time (BTT) were obtained by the sonographic device DBM Sonic BP IGEA in two sessions at two years' interval, in a school-age population (589 subjects, 290 mol/L and 299F, aged 3 to 16 y) with the aim to determine accuracy of QUS measurements, evaluate QUS variable changes during growth, relate these values with age and growth variables. Mean AD-SoS and BTT at age classes from 5 to 12 y as determined at the first and second measurement sessions were not significantly different. A significant increment (p < 0.0001) between the first and the second measurement was observed for both QUS variables. AD-SoS and BTT showed significantly different variations in the various age groups (ANOVA). Correlations were found of AD-SoS and BTT increments with age, height, weight, pubertal stage and with height growth velocity (p < 0.05). AD-SoS and BTT increment curves presented a very similar trend decreasing from 4 to 7 y of age. Thereafter a plateau was reached up to the age of 10 to 11 y in girls and 11 to 12 y in boys, when an increase was observed corresponding to pubertal growth rate acceleration. In conclusion, the present study would confirm that QUS measurements are accurate. Ad-SoS and BTT increment models are similar to most growth velocity curves and follow a strongly age- and growth-dependent pattern.