A neonate had paralysis of the right hemidiaphragm secondary to brachial plexus birth trauma. Conventional diaphragmatic plication, performed on two separate occasions, failed to correct the ventilatory impairment, and mechanical ventilatory dependence persisted. Ventilatory insufficiency was subsequently corrected by total replacement of the right hemidiaphragm with Marlex mesh. This procedure ablated paradoxical motion of the right hemidiaphragm and arrested detrimental shifts of the mobile infantile mediastinum. The good result was immediate and long-lasting; there was no major prosthesis-related growth deformity 31/2 years later. Prosthetic fixation of the paralyzed diaphragm is not indicated as a primary procedure, but should be reserved for the occasional patient in whom conventional plication has failed.