An enhanced-sensitivity immunoassay for urinary microtransferrin and microalbumin was devised based on protein precipitation with cold tri chloroacetic acid followed by dissolution of the precipitate in a small vol ume of phosphate buffer. Samples can be concentrated 10-fold by this m ethod while at the same tim e removing many of the chromogens present in urine. Concentrated samples were assayed by im m unoturbidity and radial immunodiffusion. The average recovery for urinary micro transferrin was 82 percent and for microalbumin 91 percent. The reference range for 80 normal adults for m icrotransferrinuria and microalbuminuria is 0 to 0.9 and 5 to 32 mg per g creatinine, respectively. The same m ethod can be used for the assay of other proteins such as B2-microglobulin in the urine or the cerebrospinal fluid
