In model experiments, the influence of pharmaceutical antibiotics (benzylpenicillin, pharmazin, and nystatin) in different doses (100, 300, 450, and 600 mg/kg) on a number of microorganisms of the chernozem region has been studied. All the studied doses of antibiotics had reliable and overwhelming impacts on the amount of soil microorganisms. The time between a dose of antibiotics and a change in the number of microorganisms in the soil is shown to have a linear dependence. The studied groups of soil microorganisms in relation to pharmaceutical antibiotics showed a hierarchy of resistance (high concentration): Azotobacter > amylolytic bacteria > ammonifying bacteria > micromycetes.