In a recent article M.G. Sacco and co-workers described the establishment of immortalized untransformed transgenic hepatocyte (MMH-GH) cell lines, obtained from a cross between the AT/cytoMet and Hsp70/hGH transgenic mice. This strategy proved to be successful because the MMH-GH showed stability in culture and sensitivity to chemical exposure. Based on these results, the MMH-GH cell lines could prove to be a valid alternative cell-based assay for use in toxicological studies.