Steady‐state electron flow through and electron delivery into isolated dimericbc1complex (ubiquinol–cytochromecoxidoreductase) fromNeurospora crassaand beef heart mitochondria were studied in the presence of increasing concentrations of antimycin A, funiculosin and/or myxothiazol. Parabolic or linear inhibition curves were obtained, depending upon the different quinols and inhibitors that were used. Linear curves occur when the inhibitor directly affects the rate‐determining step. The most reasonable explanation for the parabolic curves is given by a fast intradimeric exchange of the hydrophobic inhibitors antimycin A, funiculosin (rate < 500 s−1) and of myxothiazol (rate > 1 s−1). Using mitochondria from beef heart, the shape of the inhibition curve with antimycin A is parabolic if the quinol – O2oxidoreductase turns over at about 300 s−1, but hyperbolic if the rate is 5 times less. The hyperbolic titration curve may be the result of both intradimeric and an additional interdimeric redistribution (rate ∼ 100 s−1) of inhibitors between enzymes incorporated in a continuous phospholipid membrane. This explanation is supported by experiments with chromatophores obtained fromRhodobacter capsulatus. As recently described [Fernandez‐Velasco, J. & Crofts, A. R. (1992)Biophys. J. 2, A153], cytochromebbecomes fully reoxidized within 1 s after a flash at substoichiometric concentrations of antimycin A. This kinetic of the slow reoxidation can be expressed in terms of the intradimeric and interdimeric redistribution with rate constants of about 10 s−1and 2 × 106M−1s−1, respectively. It seems that rapid inhibitor redistribution may be a widespread phenomenon for hydrophobic inhibitors of enzymes incorporated in lipid membranes.