Two patients suffering from recurrent bacterial infections were studied: a boy and a girl from one family, children of apparently healthy parents. The granulocytes of these patients were capable of normal ingestion of latex particles and DNA-anti-DNA immune complexes. When the metabolic changes in these granulocytes during phagocytosis of latex particles were studied, however, no stimulation of oxygen consumption, superoxide production, or hexose monophosphate shunt activity could be observed. Moreover, zymosan particles were not iodinated. These findings are comparable to those found in chronic granulomatous disease. In sharp contrast to the observations in this latter disease, however, a completely normal stimulation of cell metabolism was found after phagocytosis of IgG-coated latex particles or IgG aggregates. Since latex and IgG-coated latex were equally well ingested, this means that the absence of metabolic stimulation after uptake of tatexf metabolic stimulation after uptake of latex must be due to a defect in the triggering of the oxidative burst. As far as we know, this is the first time that a defect in the triggering of the metabolic stimulation during phagocytosis could be demonstrated. Moreover, these finding suggest that adherence and subsequent ingestion of particles are in themselves not sufficient for the metabolic stimulation of granulocytes.