BACKGROUND: Near-infrared light (NIR, 0.8-1.5 micrometer light) has been used in therapeutic devices for various injuries such as infected, ischemic and hypoxic wound. NIR-emitting technology has been developed recently in Korea. We hypothesized that NIR may have an anti-inflammatory effect and investigated the effect of NIR-irradiated media on cell culture. METHODS: Three kinds of cell lines, CAPE (vascular endothelial cell), NIH3T3 (fibroblast), and RD (smooth muscle cell) cells were cultured for 4 days in 10% FBS-containing media (1x10(4) cells/well), which were irradiated or not irradiated (control) by Eco-NFIR Drive (Model #0210, Ecowavetech, Korea). The cells were stimulated by 10 mcg/mL of bacterial lipopolysaccharide (LPS) or sodium nitroprusside (SNP). Cellular proliferation was measured by methylthiazol tetrazolium assay. Expression of interleukin (IL)-1 beta and nitric oxide was measured by ELISA. Expression of cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS) was measured by immunofluorescence staining. RESULTS: NIR-irradiated medium was favorable for CAPE cell proliferation (N=8, P=0.000). IL-1 beta secretion from LPS-stimulated NIH3T3 cells incubated in the NIR medium was below that of control medium (N=4, P=0.026). Nitrate production seemed to be low in NIR-irradiated medium although statistically insignificant (N=4, P=0.076). Expression of iNOS of the LPS-stimulated cells was decreased in NIR medium, however, Cox-2 expression was not different between the two media. CONCLUSIONS: NIR-irradiated medium supported vascular endothelial cell proliferation and showed an anti-inflammatory effect on fibroblast culture. These results can be used as basic data for future research on the clinical application of NIR.