The study was done to determine concentrations of radionuclides and heavy metals and to evaluate the frequency of chromosomal aberrations in samples of Elodea canadensis, a submerged plant, collected in different parts of the Yenisei River. Samples were collected in the area subjected to radioactive impact of the Mining-and-Chemical Combine (MCC) at Zheleznogorsk and in the control areas, upstream of the MCC. The investigations showed that Elodea biomass in the area affected by MCC operation contained a long inventory of artificial radionuclides typical of the MCC discharges. Upstream of the MCC, in the control sampling areas, the sediments and the Elodea biomass contained only one artificial radionuclide-137 Cs. Thus, the exposure doses to Elodea shoots and roots upstream of the MCC are small (not more than 8 Gy/d) and the main contribution to them is made by natural radionuclides. At the MCC discharge site (the village of Atamanovo) and downstream of it, the total dose rate increases almost an order of magnitude, reaching its maximal values-72 Gy/d for Elodea shoots and 58 Gy/d for roots. Cytogenetic investigations of Elodea roots showed that at the MCC discharge site (the village of Atamanovo) and downstream of it the occurrence of chromosomal aberrations in ana-telophase and metaphase cells of Elodea was considerably higher than in the control area. It is highly probable that this simultaneous dramatic increase in the total exposure rate and the occurrence of chromosomal aberrations in Elodea is associated with the radiation factor. It is suggested that Elodea is affected not only by the radiation factor but also by the chemical factor-toxicity of heavy metals.