In a group of 29 infarct cases, the behaviour of the same blood and plasma viscosity at the initial stage and two weeks after the AMI was. At the same time as the rheological tests, we evaluated a few parameters of the lipid (cholesterol-triglyceride), proteic (fibrinogen) and glycoproteic (haptogloben-alpha1 acid GP ceruloplasmin) balance. Though noting significant variations of all the parameters studied, the correlation between the viscosity of blood and plasm and the other humoral parameters is of little significance. In fact except for the good correlation between the blood viscosity with hematocrit and with the fibrinogen (only on 7th day and at high gradient) the other correlations, when present, are occasional or of little significance. It is our intention to continue the research undertaken, considering either the utility of the early diagnosis of a rheological change or the possibility that the latter may be a further parameter to be related to clinical, hemodynamic and humoral parameters useful for determining the prognosis of the AMI.