In order to ascertain whether erythrocyte deformability (ED) is involved in chronic coronary syndromes, this rheological property was determined in 92 survivors of acute myocardial infarction (AMI) who had had the acute event 3 years ago and in 150 volunteers. From the 92 AMI survivors in 50 (43 males, 7 females aged 61+/-9 years) ED was determined with filtrometric techniques (Hanss Hemorheometre) and in 42 (32 males, 10 females aged 63+/-11 years) with laser diffractometric ones (Rheodyn SSD). The control group consisted of 66 and 84 volunteers whose ED was measured with the above mentioned devices respectively. Patients and controls were matched for age, sex, total cholesterol and triglyceride levels. With the Hanss Hemorheometre, the Rigidity Index (RI) was higher in patients than in controls (9.4+/-1.2 vs 8.7+/-1.5; p=0.01) although after adjusting for confounding variables (MCV and leukocyte count) in a logistic regression analysis the RI was no longer statistically significant. With the Rheodyn SSD the Erythrocyte Elongation Index (EEI) determined at 12, 30 and 60 Pa, did not show statistically significant differences between cases and controls at any of the shear stresses tested. Our results suggest that AMI survivors who had had the ischemic event 3 years ago do not show decrease RBC deformability with either of the two methodologies used. Red blood cell deformability does not appear to contribute to impaired microcirculatory blood flow in chronic coronary syndromes.