In this test, kidney-derived cells are cultured in the presence of test compounds whose cytotoxicity is then determined by the Neutral Red method, and serves as an indicator of potential nephrotoxicity (1). Healthy LLC-RK1 cells (an established cell line, ATCC CCL) maintained in culture continuously divide and multiply over time but still retain certain characteristics of kidney cells in vivo (2). Compounds that have a deleterious effect on these cells may, therefore, be considered as potential in vivo nephrotoxins. In this test system, harmful effects on cell viability are determined by monitoring the uptake of the vital dye Neutral Red into the lysosomes of healthy cells.