Single proteins and tubular enzymes have been proposed as markers to detect and differentiate prerenal, glomerular, tubular and postrenal forms of proteinuria and hematuria. By quantitation of total protein, albumin, alpha 1-microglobulin, IgG, alpha 2-macroglobulin and N-acetyl-beta,D-glucosaminidase (beta-NAG) activity it has become possible to clearly separate these forms by analysis of a single sample of second morning urine. When this program was applied to screening of hospital patients, albumin, total protein and NAG proved to be sufficient to exclude clinically relevant disturbances. alpha 1-Microglobulin was useful to separate primary glomerulopathies from tubulo-interstitial diseases. Glomerular and postrenal hematuria could be clearly separated by their different excretion rates of alpha 2-macroglobulin, if urine albumin concentration exceeds 100 mg/l. The results imply that wider application of these techniques can help to detect renal abnormalities at an earlier stage and differentiate their various forms by less invasive techniques.