Expression of bone morphogenetic protein (BMP)-2 mRNA was stimulated by retinoic acid in human adenocarcinoma cell line, HSG-S8, in a dose-dependent manner. Northern blot analysis demonstrated that retinoic acid most strongly increased the level of BMP-2 mRNA 6 h after the treatment and the stimulatory effect was maintained at 48 h. The mature peptides of 16 and 18 kDa molecular masses of BMP-2 were also increased in the conditioned medium by the treatment of retinoic acid on western blotting. The proliferation of HSG-S8 cells was inhibited by retinoic acid, however, retinoic acid did not cause morphological change showing cellular differentiation. 1 alpha, 25(OH)2D3, like retinoic acid, clearly increased the mRNA level of BMP-2, whereas dibuthryl cyclic AMP remarkably diminished it, and bromodeoxyuridine had no effect on the expression of BMP-2 mRNA.