A technique is described in which bioautograms are obtained using a human epidermoid carcinoma cell line (KB) as the indicator system. A developed papergram containing the cytotoxic material (s) is placed on the surface of a petri dish in which a KB cell sheet has been overlaid with a fortified Eagles basal medium and agar. After overnight incubation the agar medium overlay is floated off in a stream of salt solution. Continued washing removes areas of the cell sheet which have been injured by the cytotoxic agent (s) on the papergram. The treated zone can be emphasized by flooding the cell sheet with a dilute solution of trypsin. This removes injured cells which have a diminished ability to remain attached to glass and leaves healthy, unaffected cells attached. The procedure can be adapted and used as a disc plate assay procedure as is illustrated with Streptovitacin A. The utility of the tissue culture bioautographic method in the identification of cytotoxic activities originating in fermentations liquors is discussed.