A new artificial esophagus with a bilayered structure made of porous collagen sponge and silicone was studied. The concept of this study was not to replace an esophageal defect permanently with prosthesis but to promote tissue regeneration by collagen. Five centimeters of cervical esophagus were replaced by this artificial esophagus in 19 adult mongrel dogs. Two weeks after implantation, the collagen sponge was replaced by autologous tissue and regeneration of the "neoesophagus" was observed in all animals. The inner surface of the neoesophagus was covered with mature mucosal epithelium similar to the intact esophagus 4-5 weeks after implantation. The replacement site was not complicated by infection, anastomotic leakage, or exuberant granulation tissue development on the luminal surface. In a long-term survival study, animals showed moderate-grade stenosis but could take normal feed orally and with no clinical problems observed.