The inhibitory effects of fenoterol, a beta 2-adrenoceptor agonist, on the release of SRS-A leukotrienes and histamine from chopped human lung tissue were measured and selective beta-adrenoceptor antagonists used to investigate the nature of the receptors involved. Fenoterol 0.01-1.0 microM inhibited the antigen-induced release of SRS-A and histamine, but not the release induced by the calcium ionophore A23187. Propranolol 0.1 and 1.0 microM and butoxamine 10 and 100 microM significantly antagonized the effects of fenoterol 0.1 microM on SRS-A and histamine at concentrations which affect (beta 2-adrenoceptors, while atenolol 0.1 to 10 microM showed no antagonism at concentrations which affect beta 1-adrenoceptors. These results suggest that adrenoceptors in human lung which modulate the immunological release of SRS-A leukotrienes are of the beta 2-subtype as for histamine release.