In order to identify the respective roles of bile salts (BSs) which are much different depending on the species in the solubilization of cholesterol (Ch) or in the dissolution of Ch-type gallstones, the adsorption behavior of BSs on a Ch surface in aqueous media was first examined using four kinds of sodium salts: the deoxycholate (NaDC), the chenodeoxycholate (NaCDC), the ursodeoxycholate (NaUDC), and the cholate (NaC), mainly at 37°C. The adsorption behaviour of these BSs on graphite (Gr) was also examined and found to exhibit the Langmuir type isotherm, but when examined in more detail a small step was observed in each isotherm, sugesting that a certain phase transition on Gr surface or additional adsorption onto the first monolayer might take place. In the adsorption onto activated carbon (AC), the isotherms obtained for all the species outwardly exhibited the Langmuir-type adsorption and enabled us to construct Langmuir plots from which the maximum adsorption amounts of monolayer (N_m) were determined and various data derived from N_m were discussed in comparison with the corresponding data obtained for Ch and Gr. The effect of temperature on Gr was investigated for these BSs. The results were discussed by comparing among BSs as well as among adsorbent solids in terms of substantial hydrophobicity, solubilizing power and adsorption heat.