It is important to characterize possible inflammatory responses to small particles, and to separate clearly these effects from responses to larger objects nearby. This research used a chemiluminescent assay. scanning electron micrographs, and energy dispersive X-ray spectra to monitor inflammation-related reactive oxygen intermediate (ROI) production and morphological alterations of human monocyte-derived macrophages interacting with the walls of apolar and polar polystyrene cuvettes, in the absence and presence of small particles of surface-characterized Teflon(TM) polyethylene, Co-Cr-Mo alloy. titanium and alumina. The two types of polystyrene substrata represent the "bacterial" las produced) and "tissue culture" (gas-plasma-treated [GPT]) materials widely used in biological testing and tissue culture. Monocyle-derived macrophage spreading during contact with the higher-surface-energy, more polar substratum suppressed "oxidative bursts'' to lower levels than expressed from rounded cells in contact with the lower-energy, apolar substratum, Particulate matter engulfed by both rounded and spread cells did not significantly enhance ROI production beyond levels observed for no-particle controls during the one-hour exposure time. Biocompatibility of some implants might be related to cell-spreading-induced suppression of ROI production, improving the tissue integration of GPT implants.