The indications for progressive resistive strength training for prepubescent children in sports training and rehabilitation have been a source of controversy. Eighteen prepubescent children, two at Tanner Stage II and the remainder at Tanner Stage I, were studied. Examination included anthropometric upper and lower extremity strength and flexibility measurements. The study group participated in progressive resistive strength training sessions on machines three times per week. The study group had a mean increase in strength of 42.9%, whereas strength in the control group increased 9.5% (p < 0.05). The study group had a mean increase in flexibility of 4.5% compared with 3.6% in the control group. The study group showed a mean decrease in body weight during the training period of 0.51% and then gained 3.48% over the subsequent 9 weeks. The control group's body weight increased an average of 6.66% during the 18 weeks. There were no injuries during the training period. It is concluded that prepubescent children can make significant gains in muscle strength in response to progressive resistive training.