39 patients, subdivided in four groups [I) previous myocardial infarction; II) ischaemic heart disease; III) hypertension; IV) cerebrovascular disease] were administered i.v. low molecular weight dextran in the course of right heart catheterization. The curves of the left ventricular function were determined by the LVSWI-LVFP relationship measured before the test, after the first 150 ml of dextran infusion, at the point of maximal increase of the LVSWI, and at the end of the infusion. The initial values of the LVSWI and SV were lower in the first group with respect to the other three (P less than 0.001), not significantly unlike those of the LVFP. During dextran infusion it is possible to observe an increase of the LVFP in all four groups (P less than 0.01), and of the SV (P less than 0.02) and LVSWI (P less than 0.01 and P less than 0.05, respectively) in the first and the third groups. At the end of the test, different values of the LVSWI (P less than 0.001) and the LVFP (P less than 0.01) were observed in the four groups. The calculated deltaSI/deltaLVFP indices were not significantly different in the four groups, whereas a P less than 0.001 was obtained for the values of the deltaV/deltaLVFP indices (56, 67, 73 and 138 ml/mmHg for the groups I, II, III and IV, respectively). Dextran infusion proved to be a useful test for the hemodynamic assessment of different cardiovascular diseases.