Ultrasound bone measurement in healthy Croatian children and adolescents has been evaluated. Relationships between pubertal status, anthropometry, nutrition, and physical activity with ultrasound bone parameter were analyzed. A total number of 501 children and adolescents of both sexes participated in the study. There were 244 prepubertal children (120 boys and 122 girls) and 259 postpubertal adolescents (112 boys and 147 girls). Anthropometric measurements included height, weight, percent of fat tissue, and body mass index. Quantitative ultrasound measurements of the heel (nondominant side) were performed using "Sahara" sonometer and included speed of sound (SOS), broad-band ultrasound attenuation (BUA), and calculated bone stiffness (QUI). Dietary data were assessed using specially designed semiquantitative food frequency questionnaire calculations based on the daily intakes of calcium, carbohydrates, fats, and proteins. Quantitative ultrasound bone measurements (BUA, SOS, and QUI) were similar in prepubertal boys and girls. Adolescent boys had significantly higher BUA (P<.01) than girls. The percentage of children and adolescents who consumed more than 1,000 mg of calcium per day were 54.8% and 48.7%, respectively. Body weight and pubertal status and activity were significantly correlated with bone stiffness but not the calcium intake. In this study, bone stiffness in children and adolescents is determined by pubertal status and body weight, rather than by calcium intake.