Background: We investigated the effects of two antibiotics, erythromycin and rifampicin, on the immunomodulatory gene expression and cellular function of human polymorphonuclear leukocytes (PMNs). Methods: We used real-time quantitative PCR to examine the expression of immunomodulatory genes. The production of reactive oxygen species (ROS) was determined by fluorescence-activated cell sorting. PMN chemotaxis was analyzed using a KK chemotaxis chamber. Results: Stimulation of PMNs with lipopolysaccharide (LPS) resulted in increases in the mRNA levels of immunomodulatory genes. Rifampicin significantly inhibited the overexpression of TLR2, TLR4, CD14 and IL8Rs. However, erythromycin suppressed only the upregulation of TLR2 and TNFA. Neither antibiotic had an effect on the production of ROS. Rifampicin significantly inhibited PMN chemotaxis, but erythromycin had no effect. Conclusions: Erythromycin and rifampicin may play anti-inflammatory roles by affecting the expression levels of immunomodulatory genes or the chemotaxis of PMNs.