Pentraxin 3 (PTX3) is a prototype protein of long pentraxin. PTX3 is produced by various cells, such as monocytes/macrophages (Mphis) in response to lipopolysaccharide (LPS) and proinflammatory signals. We performed immunoblotting, immunohistochemical staining, reverse transcriptase-polymerase chain reaction (RT-PCR), quantitative real-time PCR and enzyme-linked immunosorbent assay (ELISA) of PTX3 in human monocyte-derived Mphis and neutrophils. PTX3 expression was observed in the cytoplasm of both GM-CSF induced monocyte-derived Mphi (GM-Mphi) and M-CSF induced monocyte-derived Mphi (M-Mphi). PTX3 level in both Mphis was up-regulated at 24 h after LPS stimulation. Moreover, we confirmed PTX3 expression in freshly isolated neutrophils, and PTX3 level was distinctly up-regulated at 6 and 24 h after LPS stimulation. These findings suggested that PTX3 expression, not only in Mphis, but also in neutrophils, may reflect the role of PTX3 in inflammation. We believe that PTX3 can contribute as a diagnostic tool to evaluate inflammation at peripheral sites.