The myocardium and blood vessels of 20 rats kept for one year on DeCarli and Lieber's liquid diet containing alcohol to 36% of total Joules were examined with routine histological, histochemical and electron microscopical methods. No changes in the gross anatomy, histology, histochemistry and electron microscopy of the arteries, veins and capillaries were found. Subcellular damage of the atrial and ventricular myocardial cells was observed. A varying number of mitochondria were affected in each of the animals: degenerated mitochondria, mitochondria with electron lucent matrix, with concentric cristae, of bell shape, with negative succinic dehydrogenase activity or vacuolated mitochondria were found. In 10% the myofibrils, and in 30% the sarcoplasmic reticulum were damaged. Secretion and lipofuscin granules increased in number in 25% of the animals. It is concluded that although the submicroscopic alcoholic alterations are similar to some of those reported in experimental ischaemia, the decrease in myocardial blood flow may not be held solely responsible for the alcoholic damages. A toxic effect of alcohol, acetaldehyde and catecholamine is postulated.