The composition of circulating immune complexes with cryo-properties (cryo-IC) were determined in 70 patients on days 1, 2, 3, 7, 14 and 21 after ischemic carotid stroke. The quantitative and qualitative assessments of cryo-IC content were conducted on a spectrophotometer and on a vertical electrophoresis, respectively. Concentrations of immunoglobulins (Ig) M, A and C, fibronectin, percentage of IgM with rheumatoid factor activity, IgG isotypes (IgG1, IgG2, IgG3, IgG4) were measured with ELISA. The control group included 15 healthy age- and sex-matched people. Compared to the controls, the cryo-IC content was higher in 100% of patients studied, it was higher in atherothrombotic variant than in cardioembolic one. The cryo-IC level was directly correlated with the clinical state severity (p < 0.01). IgG, IgM and fibronectin were observed in 100%, IgA--in 11% and IgM with rheumatoid factor activity--in 6% of patients. The percentage of IgG1 and IgG2 was not less than 90% of the total amount, with the IgG1 percentage about 50%. Cryo-IC changing in the time in dependence on ischemic variant were formed on different stages of development of acute brain ischemia. Dependence of concentrations of fibronectin and IgG, IgA, IgM on the time of observation was similar for both variants of ischemic stroke, but with a time axis shift, running faster and with a smaller range of changes of parameters studied in cardioembolic than in atherothrombotic stroke.