The changes of the rheological parameters (whole blood and plasma viscosity, fibrinogen level, red cell count, hematocrit) of 22 AMI patients (mean age: 59 years) were studied during the hospital phase of acute myocardial infarction. The measurements were carried out after the admission, after the beginning of the mobilization and before the discharge from the hospital. Looking at the results of all of the patients they could not find any statistically significant change, although in the first phase improving hemorheological parameters were measured and this way the discharge values were similar to the admission ones. In men significantly worse starting values were found than in women and the deterioration of these parameters in their group was also expressed. The deliberate use of diuretics and the administration of high dose nitroglycerin may be one part of the less worsening rheological parameters in comparison with the literature.