Aim. The analysis of toxicity of different water samples with the multibiosensor developed earlier. Methods. The potentiometric multibiosensor with several immobilized enzymes as bioselective elements and the matrix of pH-sensitive field effect transistors as transducers of the biochemical signal into the electric one was applied for the analysis. Results. The bioselective elements of the multibiosensor were developed using acetylcholinesterase, butyryl-cholinesterase, urease, glucose oxidase, and three-enzyme system (invertase, mutarotase, glucose oxidase). The measurement of toxic compounds in water samples of different origin was performed using the constructed sensor. The results obtained were compared with those obtained by the conventional methods of toxic agent’s analysis (atomic absorption spectrometry, thin-film chromatography, and atomic absorbic analyser of mercury). Conclusion. A strong conformity between the results obtained with the multibiosensor and traditional methods has been shown.