SummaryReport on a case of acute poisoning by Hg oxycyanide.Spontaneous recovery after five days of complete anuria.The restoration of the renal function was followed by :a) daily clearances of creatinine, urea, Na + , Cl—and K+ and by two functional tests measuring the inulin clearance and the renal capacity to excrete glucose at increasing plasma levels. These tests were performed on 8 successive urinary collection periods of 15 minutes. The observations were as follows :a) Creatinine and urea clearances are equal and increase simultaneouly from 0,7 and 0,52 to 23,6 and 26,4 during the 8 days following the restoration of diuresis. Thereafter creatinine clearances increased more rapidly than urea clearances.b) K clearance is the first to reach its normal value. It is higher than that of all the other components of urine during the six first days of diuresis. This fact is interpreted as a proof of the capacity of the distal nephron to secrete K.c) The amount of glucose excreted on the third day of restored diuresis remains, despite a very decreased renal function, a linear function of the plasma level of glucose. TmG = 5,28 mgr/minute. Mean threshold = 0,66. The glomerular filtration calculated from the slope of the line relating glucose excreted to the plasma level is 7,9 cc/minute. This is equal to the clearances of inulin, creatinine and urea.d) The same test performed 14 days later shows a quite different picture. TmG has a normal value 273,8 mgr/minute. Mean threshold = 2,87 gr 0,00. The appearance threshold of glucose is still decreased (1.1 gr. 0/00) and is the last remaining abnormality.e) At that time (16th day of restored diuresis) the proximal tube has recovered the ability to secrete creatinine at increased plasma levels. The ratio, creatinine clearance inuline clearance = 1,32 as compared to the value (0,89) obtained on the previous test.