A new sensitive spectrophotometric method for human serum albumin (HSA), the main protein in urine, has been developed using Erythrosin B. The proposed method is not based on conventional spectral shift but on an enhanced absorbance of the protein-bound dye and suppression of reagent blank in the presence of Triton X-100. The detection limit for HSA is 0.06 mg L-1 (S/N = 3), which is superior to conventional methods by a factor of 50-100. This is the first ever spectrophotometric method applicable for urinary protein even in healthy subjects.