This CO(2)-based tissue expansion system offers a novel and potentially valuable tool for reconstructive surgery. This study demonstrated the in vivo performance of a CO(2)-based tissue expander in an ovine model and merits future clinical research efforts. All tested devices accomplished needle-free expansion with the expanders responding to dosage-controller commands within programmed safety limitations. This system has the potential to expedite expansion through gradual, controlled distention of tissue and to simplify the process for both physician and patient.