Aim. To reveal platelet functional changes manifesting as abnormal rate of platelet aggregation in patients with acute cerebral circulatory disorders (ischemic stroke, transient ischemic attack), to evaluate the effect of homocysteine (Hc) on platelet aggregation, depending on the degree of cerebral blood flow disturbances, patients' gender and age, and to estimate the diagnostic value of their associations. Subjects and methods. 50 patients aged 33 to 98 years (mean age, 63.7±2.1 years; 20 men and 30 women) with acute cerebral circulatory disorders (18 with transient ischemic attack and 32 with ischemic stroke) were examined. The diagnosis was verified by the results of computed tomography and other clinical examinations. Adenosine diphosphate-, epinephrine-, and collagen-induced platelet aggregation was assessed in platelet-rich plasma; serum Hc concentrations were also studied. Results. Comparison of platelet aggregation and Hc concentration revealed a statistically significant correlation between platelet aggregation with collagen and elevated Hc levels (r=0.376; p<0.01). There was no statistically significant correlation with other inducers. Blood Hc concentrations increased with advancing age (r=0.357; p=0.015). No statistically significant correlation was found between age and platelet aggregation (p>0.05). The levels of Hc were statistically significantly higher as cerebral circulatory disorders progressed. Conclusion. There was a statistically significantly relationship between collagen-induced platelet aggregation and Hc concentration. The Hc levels were statistically significantly related to the severity of cerebral circulatory disorders and age.