Abstract: Tamm-Horsfall glycoprotein (THP) was prepared and purefied from urine by salt precipitation and chromatography on Sephadex G-100. An antiserum was raised by immunizing rabbits. The antiserum had a working titer of 1: 20 000 to 1: 40 000 and the affinity constant was 0.99×10~(10)l. mol~(-1). The cross reaction with β_2-MG, HSA and IgG was lower than 0.02%, 0.000 1% and 0.000 4% respectively. A RIA kit was developed for determination of THP in human serum and urine. The standard range was 50—200 0 ng/ml and recoveries varied from 96.2% to 103.9%. Intra-and Inter-assay coefficient of variation were (1.6—2.9)% and (2.3—4.2)% respectively. The normal range of THP was 123. 3±21.9 ng/ml(X±SD, n=14) in serum, and (29.0—43.9) mg/ 24 h (n=3)in urine.