Two models of experimental cardiomyofibrosis were developed: one based on a pathogenic diet, the other on administration of catecholamine. In both models marked alterations of the myocardial ultrastructure and of mitochondria were observed. However, these alterations had a microfocal character and so did not Mitochondrial respiration affect the whole myocardial mass. was decreased in the dietetic model of cardiomyopathy and increased in the catecholamine model. The P:O ratio of mitochondria as well as the content of ATP, ADP and CP in the myocardium did not reveal any significant changes in either model.