There are conflicting studies on T cell cytokine production in childhood asthma. In this study intracellular cytokine expression of IL-2, IL-4, IL-10, IL-13, IFN-γ, and TNF-α in CD4(+) and CD8(+) T cells in children with atopic asthma were measured by flow cytometry. Results. A significant increase in the percentage of CD4(+) and CD8(+) T cells producing IL-4 and IL-13 and decrease in the percentage of CD4(+) producing IFN-γ in asthmatic children was found. The percentage of CD4(+)/IL-13(+) was significantly higher in severe asthma than in children with intermittent disease symptoms. Severity of asthma was associated with increased both serum IgE and frequencies of CD4(+)/IL-13(+) T cells, as well as duration of disease. Moreover, a decrease in FEV(1), FEV(1)/FVC was observed in relation to the severity of asthma. Changes in cytokine profile in CD8(+) subpopulation didn't depend on the severity of the disease. Conclusions. Increased production of IL-4 and IL-13 in both CD4(+) and CD8(+) T cells accompanied by decreased IFN-γ expression in CD4(+) T cells may be evidence that both lymphocyte subpopulations are implicated in the pathogenesis of asthma. Relationship of CD4(+)/IL-13(+) T cells with disease activity suggests that this lymphocyte subset may have a prominent role in childhood asthma.