Activated mononuclear cells (lymphocytes and monocytes) (MNCs) circulate in peripheral blood and accumulate in the airways of individuals with steady-state asthma. The expression of adhesion molecules on MNCs of 10 patients with steady-state atopic asthma and 10 non-atopic control subjects was measured by flow cytometry. The mean fluorescence intensity of CD23 (P= 0.0003), CDl la (P= 0.034), and very late antigen-4 (VLA-4) (P= 0.016) was increased on lymphocytes of asthmatic patients relative to those of controls. Although the expression of CD16 (P= 0.002) and CD23 (P= 0.002). which are associated with differentiation into macrophages, was increased on monocytes of patients relative to those of controls, monocyte expression of VLA-4 (P= 0.006) and sialyl Lewis X (P= 0.005) was reduced. The concentration of interleukin-4 (lL-4) in serum was significantly higher in asthmatic patients than in normal subjects (P= 0.023), and a significant correlation was apparent between the serum concentration of lL-4 and the expression of VLA-4 on lymphocytes (p= 0.71, P= 0.03) or on monocytes (p=−0.72, P= 0.03) in asthmatic patients. Results suggest that lL-4 may contribute to the priming of adhesion molecule expression on lymphocytes even in steady-state conditions in individuals with chronic allergic inflammation.