The phagocyte NADPH oxidase is a crucial enzyme in the innate immune response of leukocytes against invading microorganisms. The superoxide (O<sub>2</sub><sup>-</sup>) that is generated by this enzyme upon infection is directly and indirectly used in bacterial killing. The catalytic subunit of NADPH oxidase, the membrane-bound protein heterodimer flavocytochrome b<sub>558</sub>, contains two heme moieties. Here, we first briefly discuss our recent confocal resonant Raman (RR) spectroscopy and microscopy experiments on flavocytochrome b<sub>558</sub> in both resting and phagocytosing neutrophilic granulocytes. Such experiments allow the determination of the redox state of flavocytochrome b<sub>558</sub> inside the cell, which directly reflects the electron transporting activity of NADPH oxidase. Subsequently, we report that incubation of murine RAW 264.7 macrophages with PolyActive microspheres for 1 week in culture medium leads to morphological and biochemical changes in the macrophages that are characteristic for the generation of macrophage-derived foam cells. Lipid-laden foam cells are the hallmark of early atherosclerotic lesions. Using nonresonant Raman spectroscopy and microscopy, we demonstrate that the numerous intracellular droplets in macrophages exposed to microspheres are rich in cholesteryl esters. The finding that phagocytic processes may trigger foam cell formation reinforces the current belief that (chronic) infection and inflammation are linked to the initiation and progression of atherosclerotic lesions. The study of such a connection may reveal new therapeutic targets for atherosclerosis treatment or prevention.