The purpose of the study was to determine effect of high sodium intake on fluid and electrolyte turnover and heart remodeling in the cardiac failure elicited by myocardial infarction (MI). The experiments were performed on four groups of Sprague Dawley rats maintained on food containing 0.45% NaCl and drinking either water (groups 1, 2) or 1% NaCl (groups 3, 4). Groups 1 and 3 were sham-operated while in groups 2 and 4 MI was produced by the coronary artery ligation. In each group food and fluid as well as sodium intake, urine (Vu), sodium (UNaV), potassium (UKV) and solutes (UosmV) excretion were determined before and four weeks after the surgery. Size of the infarct, left ventricle (LV) weight and diameter of LV and right ventricle (RV) myocytes were determined during post-mortem examination. Before the surgery groups 3 and 4 ingested significantly more fluid and sodium, had higher Vu, UNaV, UKV and UosmV than the respective groups 1 and 2. In groups 2 and 4 MI resulted in significant decrease in Vu, UNaV and UosmV in comparison to the pre-surgical level. In Group 4 MI resulted also in a significant decrease of food and sodium intake. The MI size did not differ in groups 2 and 4 while diameter of LV myocytes was significantly greater in groups 2 and 4 than in groups 1 and 3, and in group 4 than in group 2. The study reveals that prolonged high sodium consumption increases fluid and electrolyte turnover both in the sham and in the MI rats and that the MI causes decrease in food and sodium intake in rats on high but not on regular sodium intake. In addition high sodium diet promotes development of greater post-MI hypertrophy of the LV myocytes.