1. In the dog and monkey bilateral nephrectomy or ureteral ligation results in a marked, progressive increase of total fatty acids, of free and esterified cholesterol, of phospholipid, and of free fat of serum.
2. No such changes follow unilateral nephrectomy, splenectomy, or fasting.
3. The increase after bilateral nephrectomy is not inhibited by glucose administration.
4. A marked increase of the phospholipid and a less significant elevation in cholesterol content of the liver accompanies this increase of serum lipids after bilateral nephrectomy.