Low bone density (BD) in adolescence is a predictor for osteoporosis later in life. Although pharmaceutical regimes are available to inhibit bone loss in adults, safe, effective means of improving BD in children have yet to be defined. Short-term, low-intensity, high-frequency mechanical stimulation has improved BD and bone strength in animal models of osteoporosis. To determine the effect of this mechanical signal on children, a pilot study of 8 female subjects (mean age ± standard deviation [SD] = 9.7 ± 1.5 years) was performed. All but one subject had BD >1 SD below normal. Over 8 weeks, subjects stood for 30 minutes, 3 times/week, vibrating at 30 Hz at 0.3 g. Blood for bone-specific alkaline phosphatase (BALP) and quantitative computed tomography (CT) measurements of the lumbar spine and femurs were obtained at baseline and 8 weeks. Cancellous BD of the spine and cortical BD, fat mass, muscle mass, and cortical bone area (CBA) of the femurs were evaluated. After treatment, there was a significant increase of 6.2% in cancellous BD, 2.1% in cortical BD, and 6.1% in muscle mass. Mean BALP levels increased by 16.6%. No significant differences were found in fat mass or CBA. These results indicate that mechanical intervention may be an effective means of significantly increasing BD in children with low BD as well as increasing muscle mass at the femurs.