 In the single-center, FDA-funded trial IDE G050196, the investigators tested proof of concept, safety and probable benefit of this procedure in 10. In this Phase III multicenter trial, the investigators will further test the safety and efficacy of the procedure in 15 otherwise healthy patients with moderate-to-severe PE, ages 8 to 14. The investigators will be using the next generation Magnimplant device IDE G090006, a design the investigators believe is much improved in terms of safety and ease of implantationexplantation. Implantation of the Magnimplant will be accomplished in an outpatient procedure. The investigators will document the rate of correction by comparing chest X-ray measurement of the Pectus Severity Index prior to implantation, to that measured after the magnet is removed. Treatment will last 18-24 months, depending on correction and when the patient has completed his or her pubertal growth spurt, as documented by hand x-ray. Explant of the device will be accomplished in an outpatient procedure. The investigators will document safety with an EKG prior to implantation, one month post-implantation, and finally after the magnet is removed. The investigators will document efficacy by comparing pre- and post-treatment PSI, as well as by evaluating patient satisfaction with a post-procedure Quality of Life-type survey. Long-term follow-up will occur at 6, 12, 18, and 24 months after explantation. 