Introduction. In the scientific literature known to us, there are no experimental data on the combined human health effect of nanoparticles of selenium and copper oxides, the exposure to which is feasible in metallurgy. Materials and methods. The cytotoxic effect was modelled on outbred female rats by a single intratracheal instillation of suspended nanoparticles of selenium and copper oxides at a concentration of 0.25 mg/ml. Cytological and biochemical parameters of the bronchoalveolar lavage fluid were evaluated 24 hours after the administration of the suspension. Results. The response of the lower airways to the combined exposure to SeO and CuO nanoparticles was more pronounced than that to the exposure to either of them, thus indicating its higher cytotoxicity as judged by cytological and biochemical parameters of the bronchoalveolar lavage fluid. The combined cytotoxic effect of SeO and CuO nanoparticles was characterized by typological diversity. According to the overwhelming number of the parameters studied, the additive nature of the combined effect of high exposure doses of SeO and CuO nanoparticles was demonstrated. Limitations. The research was limited to the study of the main indicators of cytotoxic effects. Conclusion. To avoid underestimation of the cumulative health risk for workers in the chemical and slime shops of copper smelters, it is important to take into consideration the additive nature of the combined effect of toxicants under study.