The layer-by-layer interaction between bovine serum albumin BSA and sodium hyaluronate NaHA was studied by a quartz crystal microbalance QCM method. The surface structures of the BSX layer and the NaHA layer and their surface tensions were investigated using atomic force microscopy AFM. BSA showed Langmuir type adsorption on poly(gamma-methyl-L-glutamate) PMLG thin film and were found to be a monolayer in the saturated adsorption state. The adsorption of NaHA on the BSA monolayer was also the Langmuir type. From their linear reciprocal plots, adsorption constants K and saturated adsorption masses Gamma(infinity) were determined. The BSA molecules on the PMLG film surface could be imaged using AFM in the monolayer state. Furthermore. the surface structure of NaHA adsorbed on the BSA monolayer was found to form hexagonal-like networks. From the adhesion force F-ad between the AFM tip and the surfaces of the BSA layers or the NaHA layers, their surface tensions gamma(s) were estimated. The surface tension of the PMLG films increased with increasing the adsorption of BSA but the surface tension of the saturated adsorption BSA layer was found to decrease with increasing the adsorption of NaHA.