1. Chronic renal disease was produced in 235 4 to 5 week-old rats of the Long-Evans strain by the intravenous injection of nephrotoxic sera obtained from rabbits. 2. Massive proteinuria, largely without hematuria, was noted without delay. Severe edema and ascites was observed in 35% of the animals within the first 2 to 3 weeks. Thirty-two per cent died within the first two weeks. A spontaneous cure of the disease occurred in 30% and chronic renal disease that lasted in some instances as long as 13 months, was observed in the remaining animals. 3. From 125 sick rats, 74% remained normotensive. A fluctuating and moderately severe hypertension was noted in the remaining 26%. 4. The blood chemistry revealed marked hypoproteinemia and hyperlipemia in the earliest phase. This subsided slowly as the disease progressed but did not reach normal values as long as the disease persisted. With a few exceptions the creatinine concentration remained normal during all phases of the disease. Marked azotemia was frequently obtained in severe disease at onset. It subsided regularly within the first two months and slight degrees of azotemia in late stages of the disease were noted in approximately 50% of the rats. 5. A histologic analysis was obtained in 119 sick, 12 recovered and 31 control rats. By correlating the chronologic order of clinical evidence with the pathologic picture, the following conclusions were drawn: (a) The nephrotoxin produces primarily a degenerative lesion with changes in glomeruli and tubules; (b) There may be recovery from the degenerative phase or it may be followed at variable intervals by a variable degree of fibrous proliferation in the glomerular tufts and capsules.