Adult human and rabbit Fallopian tube fragments, which maintained in in vitro cultures their specific histological structure and coordinated vibratory activity, were submitted to infection with polio, adeno, bovine rhinotracheitis, herpes and other viruses. The organized ciliated epithelium when compared with undifferentiated epithelium in in the same cultures showed in all cases a relative resistance to the cytopathic action of viruses, manifested by a marked delay in cell destruction, more pronounced in the case of bovine rhinotracheitis or polio and less marked in the case of herpes or vaccinia viruses. This resistance could not be abolished either by immobilization of cilia with anesthetics or by treatment of cell surface with hyaluronidase or trypsin. Thus the resistance phenomenon observed previously with respiratory ciliated epithelia appears to be a more general one, concerning a class of epithelial cells preserving their supracellular organization in vitro. This may be an illustration of the variety of cell-virus reactions with differentiated and specialized animal cells, much wider than that established for monocellular organisms and their viruses. - -Authors.