The results of assessing the state of surface water bodies located in the zone of influence of the closed landfill of industrial and household waste "Shcherbinka" (Domodedovsky district of the Moscow region) are presented. The toxicity of river and waste waters of the landfill was determined by the biological effect on two species of higher plants – oats sowing (Avena sativa) and watercress (Lepidium sativum). As test reactions, the length of the roots of oat seedlings, the germination and length of seedlings of watercress seeds were used. It was found that wastewater from the surface and body of the landfill has a pronounced phytotoxic effect (52–98 %), which manifests itself in the suppression of all the assessed indicators. The high toxicity of river water in the place of discharge of leachate from the waste disposal facility was shown (the phytoeffect value reaches 37 %). As you move away from the source of pollution (when moving downstream of the river), mixing the leachate with river water reduces the concentration of chemicals in the waters to levels that are safe for plants. The values of the estimated indicators obtained during biotesting of river waters at a distance from the landfill are comparable with the control ones. The experiment revealed a similar sensitivity to toxicants of two plants selected as test objects.