The cytotoxicity of four aminoglycoside antibiotics was studied by estimation of the dose-effect relationship using a panel cellular biotest system including cell cultures for test objects. The cultures represented 4 differentiation types: normal human fibroblasts and myoblasts, human or Syrian hamster hepatoma cells, and mouse/mouse hybridoma cells. It was found that three widely used antibiotics gentamicin, kanamycin, and neomycin exhibit similar, but not identical cytotoxicity parameters and differ distinctly from geneticin. Hence, the proposed panel biotest system helps to quantitatively evaluate and differentiate the effects of bioactive substances with similar chemical structure.