This study was design to investigate the “in vitro” effect of bisphenol A (BPA), a component of resin used in dentistry, on viability, and substrate adherence capacity of macrophages. Peritoneal macrophages were obtained from Wistar rats and resuspended in RPMI-1640 medium. Viability was determined by trypan blue exclusion. As a test of macrophage adhesion, the adherence capacity of macrophages to a plastic surface was determined and the adherence index was calculated. Assays were conducted in Eppendorf tubes for 60 min of incubation at 37°C in a humidified atmosphere of 5% CO₂ in air. BPA did not alter significantly macrophage viability at concentrations as high as 10⁻⁵M, but BPA decreased in a dose-dependent manner the adherence index of rat peritoneal macrophages. Control peritoneal macrophages showed an adherence index = 81.5 ± 7.9%. In the presence of 10⁻⁸M BPA, the AI of macrophages decreased to 41.4 ± 12.2% (p < 0.05). Higher BPA concentrations (10⁻⁷ to 10⁻⁵M) also caused a significant inhibition of the adherence index. Half-maximal inhibition (IC₅₀) was obtained at 4.92 ± 0.39 × 10⁻⁶M BPA. The in vitro study shows that the resin component BPA can alter macrophage adhesion. Taking into account that adhesion is the first step in the phagocytic process of macrophages and in antigen presentation, BPA could inhibit macrophage function and modulate immune and inflammatory responses in dental pulp and periapical tissues.