The effect of prolonged (14 days) passive smoking on the respiration of isolated cardiomyocytes in rabbits using various substrates (pyruvate, glutamate, succinate) was studied. The endogenous respiration of cardiomyocytes was not affected whereas stimulated respiration as well as the ratio of stimulated to endogenous respiration significantly decreased. These results complement previous studies in which the effect of smoking on the metabolic processes of heart muscle mitochondria was measured. In conclusion, prolonged smoking may provoke myocardial dysfunction and in this way may contribute to the development of heart failure in chronic smokers.