The relationship between filtration rate (GFR) and electrolyte excretion was investigated during infusions of low doses of angiotensin II (0.02 to 2.0 µg/sq m/min) by means of repeated clearance experiments in trained normal, adrenalectomized, and chronic experimental renal hypertensive dogs. A limited number of experiments were conducted also in dogs anesthetized with pentobarbital. Parameters of BP, C<sub>In</sub>, C<sub>pAH</sub>, U<sub>Na</sub>, and U<sub>k</sub> were determined simultaneously under conditions of a moderate water diuresis. Alterations in GFR were produced by varying the dose of angiotensin, thereby allowing a study of electrolyte excretion under conditions of decreased, relatively unchanged, and increased filtered loads. The data was grouped for statistical analysis on the basis of whether the change in GFR from control was more than –5%, within ± 5%, or above +5%. Sodium excretion (U<sub>Na</sub>V) was found to parallel the change in GFR in the three types of dogs. Potassium excretion (U<sub>k</sub>V) showed also a relationship with GFR in the normal and hypertensive dogs but fell significantly below control in the adrenalectomized dogs when GFR remained at control levels (within ± 5%). Significant alterations in tubular sodium transport were not apparent at the low doses of angiotensin used in this study. A dampened renal vasomotor response was observed in the hypertensive dogs which was associated with a greater tendency of GFR to increase above control. It is concluded that under the conditions of this study low doses of angiotensin can produce a decrease, no change, or an increase in the excretion of sodium as a result of the drug’s action on the renal vascular bed to alter GFR.