A rapid method for nearly quantitative isolation of human serum albumin is described. The present technic (1) is a modification of the Schwert method (2). In the present method 4 ml. of serum is precipitated with trichloroacetic acid in a final concentration of 5% (w/v). The precipitate is washed with TCA, and after aqueous suspension, ethanol is added to a final concentration of 80%. The undissolved globulin is washed with ethanol and the solubilized albumin used for quantification, characterization, and isotope counting. Recovery of added human serum albumin was approximately 98%; recovery of added 131I albumin was 90%. Cellulose acetate electrophoresis showed a single band, and agar diffusion produced one precipitate line. Immunoelectrophoresis with anti-human serum revealed one or two very faint arcs in the α-, or α- and β-globulin regions, in addition to the major arc of albumin. The method has shown excellent reproducibility in replicate analyses of normal and pathologic serums.