The problem of pollution of aquatic environment by pharmaceuticals and theirs metabolites is not enough known and appreciate in Poland. Presence of drugs in water, even in small concentration, can carry real consequences for aquatic organisms, disturb biological balance in ecosystem and even it can have an impact on a human health. Many active substances contained in pharmaceuticals are degradating very slowly in aquatic environment. Due to their lipophilicity, they can easily accumulate in tissues of aquatic organisms. In the aquatic ecosystems drugs occur in mixtures with other substances, what makes difficulties in proper assessment of their real impact on the environment. Indeed, these compounds may mutually induce or suppress their toxic effects. During presented research were used occurring in flowing waters crustaceans Gammarus varsoviensis. The aim of this study was to comprehensively evaluate the usefulness of scuds as bioindicators of water pollution by drugs. Fluoxetine (antidepressant), propranolol (antiarrhythmic drug) and various mixtures there of are used in the research. During the research the acute toxicity of mentioned substances were analyzed – according to Polish Standard. The growing relationship between the mortality of tested organisms and the concentration of tested compounds was established. The increase of toxicity of the tested drugs in its mixture was also observed.