We describe a gel-supported in vitro system for culturing skin samples in a three-dimensional native state. All the cell types of skin remain viable and maintain their native architecture for at least 10 days. The culture system is used for toxicity measurements by ascertaining cell viability using two fluorescent dyes: 2',7'-bis-(2-carboxyethyl)-5-(and -6)carboxyfluorescein acetoxymethyl ester, specific for living cells, and propidium iodide, specific for dead cells. Cell staining with the dyes is measured throughout the tissue block by confocal scanning fluorescence microscopy. The dose-response to three agents--ethanol, doxorubicin, and sodium hypochlorite--is shown and, in the case of sodium hypochlorite, compared to in vivo skin toxicity with a high correlation. We also demonstrate that the end point of [3H]thymidine incorporation measured by histological autoradiography can be used to measure toxicity. Our results with the [3H]thymidine end point demonstrate that the hair follicle cells are the most sensitive to doxorubicin. The native-state model for skin may be an effective replacement for animal systems and superior to the dispersed skin cell systems used previously. It can allow rapid, inexpensive measurements of the effect of manufactured products, drugs, and pollutants on skin.