AIM To study the regulatory effects of osthole on function of osteoblast. METHODS Osteoblastic cells were isolated from newborn rat calvaria through trypsin digestion. The proliferation of osteoblasts was assayed by 3H TdR.Levels of NO, IL 1 and IL 6 in the supernatant of rat osteoblast were determined by Griess agents, examing proliferation of thymic cells and bioassay B 9 cells as target cells. RT PCR analysis was used to determine the expression of IL 6 mRNA by osteoblast. RESULTS Osthole significantly inhibited the production of NO, IL 1 and IL 6 by osteoblast spontanously or induced by cytokines and LPS from osteoblast. It also inhibited the expression by IL 6 mRNA by osteoblast. CONCLUSION Osthole could regulate the function of osteoblast by reducing the production of NO, IL 1 and IL 6.