The effects of various kinds of growth factors or steroids on the proliferation of Shionogi carcinoma 115 (SC115) cells were investigated in cell culture. In a serum-free medium [Ham's F-12:Eagle's minimum essential medium (1:1, vol/vol) containing 0.1% bovine serum albumin], the proliferation of SC-3 cells (a cloned cell line from SC115 cells) estimated by [3H]thymidine incorporation into DNA and cell number reached a plateau at 10(-8) M testosterone (up to 200-fold), 10(-7) M dexamethasone (up to 30-fold) or 1 ng/ml of fibroblast growth factors (FGF; up to 50-fold). However, the proliferation in the serum-free medium was not significantly stimulated by the addition of low to very high concentrations of progesterone, oestradiol-17 beta, epidermal growth factor, platelet derived growth factor or insulin; transforming growth factor beta slightly stimulated the growth (up to 5-fold) but markedly inhibited the growth stimulation induced by testosterone. Furthermore, an epithelial appearance of SC-3 cells grown in the absence of growth factors or steroids was changed to a fibroblast-like appearance only by the addition of testosterone, high concentrations of dexamethasone or FGF. By investigating various kinds of growth factors or steroids, the present study demonstrates that androgen, high concentration of glucocorticoid or FGF alone significantly stimulates the proliferation of SC-3 cells with a change of morphology in the serum-free medium.