We report a reversed-phase "high-performance" liquid-chromatographic assay for beta 2-microglobulin, alpha 1-acid glycoprotein, and albumin in urine. The urine samples are chromatographed on a 15 X 3.2 mm C18-column with a solvent gradient between two mixtures: 1 mL of trifluoroacetic acid per liter of water and 1 mL of trifluoroacetic acid per liter of acetonitrile. The proteins are detected at 218 nm. The useful lower limit of sensitivity for quantification is 0.1 micrograms of each protein in 100-microliters injected samples, corresponding to 1 mg of protein per liter of urine. The linear measuring range extends from 0.1 to 100 micrograms of protein for each peak. Mean analytical recoveries ranged from 92 to 100%. The mean within-assay CV was 7.5%, the between-assay CV 15%. Comparison of results with those obtained by immunoturbidimetry and radioimmunoassay shows acceptable correlation. Reproducible and rapid with low operational cost, this method is suitable for use in routine screening and quantification of urinary proteins.