The branching of the electron flow to individual teminal acceptors NO3−, NO2− and N2O was investigated in denitrifying cells of Paracoccus denitrificans. It was found that the extent of electron flow to nitrate depends on the activity of electron flow through the terminal part of the respiratory chain comprising cytochrome c.NO2− and N2O either endogenously formed or exogenously added decreased the rate of nitrate reduction by oxidizing the respiratory chain via nitrite reductase and nitrous oxide reductase. The inhibitory effect of both intermediates of denitrification was released by antimycin. The rate of the first reaction of the sequence NO3−→ NO2−→ N2O → N2 is in the type of cells used under feedback redox control exerted by concentration of intermediates. This regulation can be designated as ‘inhibition by product via respiratory chain’.The reaction rate of nitrate denitrification could also be influenced by changing the portion of electron flow from substrate to cytochrome c by artificial electron acceptors and donors. By varying the concentration of N,N,N′,N′‐tetramethyl‐p‐phenylenediamine in the presence of ascorbate, the desired redox state of cytochrome c and consequently various rates of nitrate reductase activity could be established. The basis of the enhancing effect of dithionite on the rate of nitrate reduction could also be explained by its functioning as an electron donor for the terminal part of respiratory chain.The quantitative evalution of the extent of electron flow revealed that both branches of the respiratory chain (to nitrate reductase and to cytochrome c) compete for a constant limited flow of redox equivalents supplied from dehydrogenases. A strong evidence exists that the same mechanism is implied in the inhibition of nitrate reduction brought about by oxygen.