The bovine heart mitochondria were separated by centrifugation and the saponins of the herbs ginseng, bellflower, and Codonopsis lanceolate were fractionated by a solvent partition. NADH oxidations were assayed in terms of 340 nm absorption decrease when the electron transport system contained the saponins. In this assay some typical surfactants dodecyl sulfate, deoxycholate, and Triton X-100 were also used for comparison. In general, the electron transport from NADH to $O_2$ was improved when $10^{-7}-10^{-5}M$ saponins or surfactants were added to the reaction systems. However. gradual decrease in the mitochondrial activity was observed as the concentration of the saponins as well as the typical surfactants was increased up to $10^{-4}M$ for example. In the cases of the pretreatment of the mitochondria with the saponins or surfactants, the oxidation rates were decreased. Increase in concentrations of exogenous cytochrome c contributed proportionally to the rate increase. The activity of a purified cytochrome oxidase was considered to be somewhat affected by the saponins or the surfactants. It is considered that the activation of the electron transport by the saponins may be caused by an increase in mobility or fluidity of the cytochrome. while the deactivation of the transport may be by an elimination of the cytochrome. Added NADH. cytochrome, and the saponins/typical surfactants may contact with the inner membrane of the mitochondrion. These mobility increase and elimination of the cytochrome may largely be attributed to the surface activity of the saponins from the plants including the ginseng.