We have undertaken a double blind placebo controlled study of disodium cromoglycate (DSCG) in 32 symptomatic young smokers. These individuals had regular morning cough and sputum with the sensation of wheeze, but were not asthmatics as determined by the usual criteria. No significant changes were observed in sputum or serum eosinophils, IgE, IgG or IgA, or sputum histamine concentrations following the administration, for 3 weeks, of either DSCG (20 mg) or placebo, thrice daily. However DSCG, but not placebo, was associated with significant improvements in the symptoms of cough (P less than 0.01) and wheezing (P less than 0.025). We suggest that these changes may be due to an effect of DSCG on the irritant receptor mediated reflex response to cigarette smoke rather than the involvement of mast cells.