Rats were treated with a single intravenous injection of thorotrast (thorium dioxide)--the source of alpha-rays. Dynamic investigation of urine protens of rats by methods of electrophoresis and immunoelectrophoresis was carried out during 22 months after thorotrast injection. Already the month after drug injection the selectivity of tubular reabsorbtion was disturbed. Three months after thorotrast injection the content of urinal proteins of tissue (in particular renal) origin was decreased. Finally the selectivity of renal filtration of proteins was damaged 4-6 months after thorotrast introduction. Serum proteins which were absent in normal urine (for example transferrin and lipoproteins) appeared in urine of affected rats. The urine proteins of serum origin were less degraded than those in normal urine. The alterations of glomerular filtration was increased up to 20-22 months when the spectrum of urine proteins became similar to the spectrum of serum proteins. The death of treated rats was occurred in this period. Thus the monitoring of urine proteins of rats treated with alpha-ray producing preparation throtrast allows to register the successive alterations of reabsorbtion, excretion and filtration functions of kidney.