Biochemical characteristics of 6 alpha-methylhydrocortisone 1-en-dehydrogenation by bacterial cells of Arthrobacter globiformis 193 have been studied. The reaction follows the kinetics of substrate inhibition; the inhibition reveals itself at the level of the respiratory chain. A mathematical model describing multiple substrate inhibition during the process of 6 alpha-methylhydrocortisone 1-en-dehydrogenation with whole cells was proposed The solution of the constructed model agrees well with experimental data. There is little or no inhibitory effect at low substrate concentrations, and the reaction rate is determined by the enzyme-substrate interaction rather than the respiratory chain activity.