The simultaneous effect of passive smoking and alcohol on oxidative phosphorylation was studied in rabbits after 14 day exposure. The results were compared with those obtained in previous studies on the isolated noxious effect of smoking or alcohol. The authors conclude that under the given experimental conditions the combined effect of ethanol and smoking doses not affect oxidative phosphorylation of mitochondria: energy production and respiration of mitochondria were preserved. The protective effect of ethanol upon the harmful effect of smoking on mitochondrial oxidative phosphorylation is accounted for by potential interaction of nicotine and ethanol in the microsomal fraction of the liver.