The Chinese diet is low in calcium, including among adolescent girls, with an average intake around 500 mg per day. In this study, we compared the percentage change in bone mineral density and content of the spine and hip region in a 1-year follow-up study between 104 adolescent girls aged 14 to 16 years receiving 375 ml calcium-fortified soymilk supplementation and 95 girls in the control group. The mean percentage changes of bone mineral density/content (BMD/BMC) and standard deviation (SD) at 1 year for the supplementation and control groups were as follows: neck of the femur BMD 2.7+/-2.94%, 1.8+/-3.49% (P = 0.08); trochanter BMD 3.3+/-3.27%, 1.6+/-2.94% (P < or = 0.001); intertrochanter BMD 3.6+/-3.05%, 2.32+/-2.95% (P = 0.002); total hip BMD 3.1+/-2.39%, 2.05+/-2.22% (P = 0.001); total hip BMC 3.8+/-3.05%, 2.6+/-2.96% (P = 0.006). The percent difference between the percentage of bone changes in the supplementation and control groups [100x (soymilk-control)/control] ranged from 45 to 113%. We observed no differences in the spine BMD/C and no differences in changes of height and weight between the soymilk supplementation and control groups, which yielded similar results. Stepwise multivariate regression analysis including height, weight, growth stage, dietary energy, protein, calcium from usual diet and physical activity also showed that supplementation was significantly associated with a percentage increase in BMD/C at the hip. We conclude that 375 ml calcium-fortified soymilk supplementation, or an equivalent of about two glasses, is among the effective strategies for bone acquisition and the optimization of peak bone mass in adolescent girls.