The regulation of intestinal cell proliferation, migration, and differentiation has been the subject of numerous studies. However, in human, progress in this field has been traditionally hampered by the lack of normal epithelial cell models. The aim of the present study was to define conditions in order to isolate, and more importantly to grow in a continuous manner, human small intestinal epithelial cells. A number of mechanical and/or enzymatic dissociation methods have been tested to isolate viable epithelial cells from the fetal small intestine. Cultured cells were characterized by indirect immunofluorescence and Western blot analysis. It was found that the use of thermolysin (50 microgram/ml, 2-3 h at 37 degrees C) can be advantageously applied to the isolation of viable epithelial cells free from contaminating fibroblasts when obtained from the 17- to 19-week fetal ileum. Furthermore, this procedure allowed the generation of continuously growing human intestinal epithelial cell cultures, which retain the ability to express specific cytokeratins as well as intestinal cell markers over a number of passages. This study shows that normal epithelial cell cultures can be relatively easily and reproducibly generated from the human fetal small intestine.