The study was aimed at measuring the number of CD38+ lymphocytes in peripheral blood and its relationship with a marker of endothelial dysfunction CD31/PECAM-1 in patients with moderate or severe bronchial asthma (BA) during exacerbation and 12 months after it. The study groups included 153 patients, the control one consisted of 40 subjects. Group 1 comprised 106 patients with moderate BA, group 2 patients with severe steroid-independent BA (n=61), group 3 patients with steroid-dependent BA (n=53). CD38+ lymphocytes were detected by immunocytochemical methods, IL-6, IL-4, IL-2, and TNF-α by solid-phase immunoenzyme assay. BA patients exhibited signs of systemic inflammation reflected in the two-fold and 2.5-fold increase of serum TNF-α and IL-6 levels respectively in the patients of group 1. TNF-α, IL-6 and C-reactive peptide levels increased by 3, 2 and 2.5-4 times in groups 2 and 3. Exacerbation of BA resulted in a 5-fold rise in the number of DC38 lymphocytes that persisted during the next 12 months suggesting a 15% increase in the level of sPECAM-1/sCD31 (a non-substrate ligand of CD38) associated with endothelial dysfunction. The study revealed positive correlation between elevated sPECAM-1/sCD31 levels and the number of CD38+ lymphocytes in all groups (r=0.456; p<0.05).