Abstract The effects of acrolein and methylvinylketone on some mitochondrial processes have been studied. The respiration with various substrates is inhibited. The sensitivity to acrolein decreases in the following order: ADP-stimulated respiration with glutamate, DNP-stimulated respiration with glutamate, ADP-stimulated respiration with succinate, DNP-stimulated respiration with succinate and respiration with NADH of aged mitochondria. It is suggested that acrolein acts on three different sites; glutamate transport, Pi transport and succinodehydrogenase. The effect on Pi transport is competitive with respect to Pi. Methylvinylketone shows the same effects as acrolein, however, it is less effective by one order of magnitude.