There is provided an in vitro assay for screening a test compound for toxicity in renal proximal tubular cells. The method comprises contacting a test compound with a test population of renal proximal tubular cells; and examining one or more cell morphology features, examining one or more cytoskeleton features, and/or determining cell numbers of the renal proximal tubular cells in the test population and comparing such cell morphology, arrangement of cytoskeletal components and/or cell count with the respective features of a control population. A change in one or more cell morphology features, a change in arrangement of one or more cytoskeleton features or a decrease in cell numbers of the test population relative to the control population is indicative that the test compound is toxic for renal proximal tubular cells.