Fluorescence photobleaching recovery was employed to investigate the relationship between the activation of neutrophil NADPH oxidase and lateral mobility of membrane proteins. Treatment of neutrophils with the crosslinking reagent disuccinimidyl suberate (DSS) blocked activation of the respiratory burst without affecting the lateral motion of concanavalin A receptors. Neutrophils treated with DSS after prestimulation with concanavalin A generated superoxide in response to another stimulator, phorbol myristate acetate, in spite of the lateral immobilization of concanavalin A receptors. The apparent lack of correlation between the activation of NADPH oxidase and the lateral motion of membrane proteins is discussed.