The aim of the study was to compare morphological and rheological properties of blood of long distance runners and untrained men. The study was carried out on 20 healthy males of age about 60 years old: 10 long distance runners and 10 untrained men. There was no difference between compared groups in age, body height and body weight. Venous blood for rheological, morphological and fibrinogen analysis was sampled in the morning time. Comparison of trained men to untrained men showed higher mean values of erythrocyte elongation index at shear stress levels from 2.2 Pa to 60.0 Pa in trained men. We observed no differences in mean values of aggregation indices (AI, %), the half time (T1/2, s) and amplitude and total extent of aggregation (AMP, arbitrary units) between groups. In both groups mean differences of morphological parameters of blood were not statistically significant. In a group of long-distance runners the level of fibrinogen was lower than in a group of untrained men. The study revealed modulating effect of physical activity on haemorheological properties of blood.