In this study we investigated a phenotype of intact and PHA-stimulated T-lymphocytes from peripheral blood of patients with allergic and nonallergic asthma. Expression of the activation markers (CD25, CD71, HLA-DR) on subsets of T-lymphocytes (CD4+ and CD8+) was determined using double-colour flow cytometry. It was found that nonallergic patients had increased percentages of CD4+CD25+, CD8+CD25+, CD4+HLA-DR+, CD8+HLA-DR+ cells. Allergic patients had a significant increase of CD4+CD25+ cells only. To examine functional significance of these changes mononuclear cells were cultivated with PHA in vitro. Thus, our findings improve our knowledge about asthma pathogenesis and create the grounds for pathogenetically validated immunocorrection.