1. Angiotensin blood levels (ABL) have been measured in thirteen white patients with diagnoses of acute renal failure of different aetiologies during several stages of the disease and with no evidence of other conditions that could stimulate renin release by the kidney.
2. Mean ABL on admission was 770 SEM 62 ng/l. When daily urinary volume was higher than 1500 ml, these values were significantly lower: 114 SEM 49·6 ng/l.
3. A negative correlation between ABL and systolic blood pressure was obtained (r = −0·35, P = 0·01). The partial correlation coefficients between ABL and systolic blood pressure showed the same results.
4. A negative correlation between the logarithm of ABL and daily urinary volume was obtained. The partial linear correlation coefficients between ABL and urine volume confirmed this relationship.
5. There was no correlation between the ABL and the aetiology of the anuria, its final course, the duration of the disease, the arterial blood pressure and the plasma urea, sodium or potassium levels.
6. It is suggested that the decrease in the ABL has some connection with the re-establishment of the diuresis, possibly through an increase of glomerular filtration rate and in sodium excretion affecting the macula densa cells.