The purpose of this work is to evaluate the activity of vasodepressor lipid (VDL) isolated from kidneys of rats with experimental hypertension at different stages of the disease, and to compare it with the renin content in the kidneys. The results show: 1. The content of renin in the ischemic kidney of rats with renal hypertension increases during the acute phase of hypertension (while the intact kidney has not yet been removed), but thereafter it drops to or below the initial level. 2. The quantity of VDL in the ischemic kidney increases simultaneously with the quantity of renin during the first days after the onset of hypertension, but later, though the renin content drops, the content of VDL remains increased.