N-ethyl-N-hydroxyethylnitrosamine (EHEN), a member of the nitrosamine class of carcinogens induces renal cancer. However, since very little is known about the metabolic products of EHEN and their effects, these were investigated in rats and mice. EHEN, N-ethyl-N-formylmethylnitrosamine (EFMN) and N-ethyl-N-carboxymethyl-nitrosamine (ECMN) were administered in the drinking water for 2 weeks and the animals were then maintained until sacrifice at week 32. The urine of the rats was collected over the 2-week exposure period and analyzed by HPLC. The results showed that EHEN but not EFMN or ECMN induces tumors in the kidneys of rats. In mice the lungs were targeted not only by the parent compound but also by both metabolites. The findings suggest that the kidney is the most susceptible organ to EHEN effects in the rat while the lung is the most susceptible organ in mice. These results are consistent with inter-species variation in the metabolism of xenobiotics.