The IgE-dependent stimulation of mononuclear phagocytes and blood platelets can be measured by antiparasite cytotoxicity, oxygen-mediated chemiluminescence and, in macrophages, lysosomal enzyme activity. Using these parameters, the present study demonstrated an inhibition by nedocromil sodium of the IgE-mediated triggering of the nonmast cell inflammatory populations in the rat. These observations suggest that nedocromil sodium may be of value in the modulation of IgE-dependent cell activation inducing the release of inflammatory mediators.