Many cell populations are thought to be involved in the etiopathogenesis of bronchial asthma. We examined by flow cytometry the relative and absolute number of CD3+, CD4+, CD8+, alpha beta TcR+ or gamma delta TcR+ T cells, CD19+ B cells; and CD56+ natural killer (NK) cells in the peripheral blood of 26 adult patients with difficult-to-control asthma (DCA) and 22 patients with minimally symptomatic asthma (MSA). Statistically higher relative and absolute numbers of NK cells (18.39 +/- 10.67% and 0.38 +/- 0.17 x 10(9)/l) in comparison with healthy controls (11.77 +/- 8.06% and 0.25 +/- 0.19 x 10(9)/l) and significantly decreased relative and absolute numbers of gamma delta T cells (3.02 +/- 2.16% and 0.06 +/- 0.04 x 10(9)/l) in comparison with controls (5.65 +/- 2.90% and 0.13 +/- 0.08 x 10(9)/l) in the DCA patient group were found. After pooling of data from both MSA and DCA patients and dividing the patients according to the presence of allergy, the relative and absolute numbers of gamma delta T cells were found to be diminished in both the allergy (3.77 +/- 2.98 and 0.07 +/- 0.05 x 10(9)/l) and nonallergy (3.06 +/- 1.78% and 0.06 +/- 0.03 x 10(9)/l) groups in comparison with healthy controls. The reason for the low number of gamma delta T cells in the peripheral blood of patients suffering from bronchial asthma is under investigation.