Chromones are frequently employed in the treatment of allergic rhinoconjunctivitis and asthma. Following our recent investigations concerning the influence of some antiallergic drugs, such as cromoglycate sodium, steroids, oxatomide and ketotifen (H1 antihistamines), and theophylline, on the immune response, in the present study we analyzed the in vitro effects of a new chromone derivative, nedocromil, on the immune response. To this end, the proliferation of peripheral mononuclear cells (PMNCs) induced by mitogen (PHA) and by CD3, CD2 or CD28 monoclonal antibodies (MAbs) has been studied. Since the effects of nedocromil on immunological parameters are achieved at 10(-7) mol/l, in the experiments herein reported the drug was tested in the cultures at concentrations of 10(-8), 10(-7) and 10(-6) mol/l. Furthermore, the effect of nedocromil was evaluated on the surface expression of the following markers expressed by PMNCs upon activation: ICAM-1 (CD54), LFA-1 and alpha 1-acid glycoprotein (alpha 1-AGP). The results of the present investigation showed no effect of nedocromil on these immunological parameters. These data acquire clinical relevance when related to previous reports showing a depression of the immunological response exerted by other compounds, such as ketotifen, theophylline and steroids.