We have been developing an artificial esophagus constructed of autologous esophageal component cells by cell culture. Because human esophageal epithelial cells are stratified in 20 layers, we attempted to construct an artificial esophageal epithelium 20 twenty layers thick. In in vitro experiments, we investigated how keratinocyte growth factor produced by fibroblasts accelerates the proliferation and differentiation of epithelial cells. Esophageal epithelial cells were cultured on collagen sheets in which dermal fibroblasts (0, 1, 4, 8 x 10(5) cells/ml of collagen) were embedded. In cultured epithelial cells on collagen gels without fibroblasts, 2.1 layer stratification was observed on the 21st day. With 1 x 10(5) fibroblasts/ml of collagen, 3.0 layer stratification was observed, 5.0 layers with 4 x 10(5) fibroblasts, and 18.1 layers with 8 x 10(5) fibroblasts. The degree of epithelial cell stratification was thus correlated with the number of embedded fibroblasts. Tubes constructed of a polyglycolic acid mesh frame, a collagen layer with esophageal fibroblasts, and an inner layer of esophageal epithelial cells were transplanted into muscle flaps of athymic rats. The luminal structures were observed to be patent without stenosis for 14 days. Histology of the epithelium revealed 20 layers of stratification. We thus succeeded in constructing epithelium similar to human esophageal epithelium. In the future we will attempt to use the tubular structures as a substitute for the esophagus after esophagectomy.