Theasinensin A is one of the oolong tea theasinensins, which differ from green tea catechins and black tea theaflavins. In a previous study, we found that theasinesin A had a potential effect on antiinflammation since theasinensin A suppressed LPS-induced COX2 and PGE(2) production. To clarify the molecular mechanisms, we investigated the gene expression profiling in macrophage-like cells treated with theasinensin A through a genome-wide DNA microarray in the present study. Among 22,050 oligonucleotides, the expression levels of 406 genes were increased by ≥3-fold in LPS-activated RAW264 cells, 259 gene signals of which were attenuated by theasinensin A treatment (≥2-fold). Expression levels of 717 genes were decreased by ≥3-fold in LPS-activated cells, of which 471 gene signals were restored by theasinensin A treatment (≥2-fold). These genes were further categorized as "defense, inflammatory response, cytokines activities, and receptor activities," and some of them were confirmed by real-time polymerase chain reaction. Furthermore, pathways analysis revealed that theasinensin A regulated the relevant expression networks of chemokines, interleukins, and interferons to exert its antiinflammatory effects.