Nephrotoxicity is a relatively common and potentially serious adverse effect of treatment with certain cytotoxic drugs (especially ifosfamide). The patient may develop severe chronic proximal tubular toxicity. It is therefore very important to attempt to reduce the frequency and severity of acute and chronic nephrotoxicity resulting from chemotherapy. A logical approach is described, with particular reference to ifosfamide and cisplatin, involving improved evaluation of the important clinical features of nephrotoxicity and a greater understanding of its pathogenesis. This approach will facilitate the development of logical preventive strategies, or less toxic analogues, or both. The methods used may also enable prediction of the potential nephrotoxicity of newly developed cytotoxic agents.