A new method of quantitative determination for serum albumin in aqueous solution has been developed by measuring total internal reflection synchronous fluorescence at the solid/liquid interface. The combination of bovine serum album in (BSA) and mesotetrakis (4-sulphonatophenyl) porphyrin (TPPS) adsorbed onto the glass surface produced a synchronous fluorescence signal at 421 nm. At pH 4.25, the signal intensity of BSA adsorbed on the interface was proportional to the BSA concentration in bulk solution. The linear range of 1.0-8.0 microg x mL(-1) and the detection limit of 0.94 microg x mL(-1) were obtained. The human serum samples were determined with satisfactory results.