The direct action of angiotensin II on renal glomeruli was quantified by measuring extracellular space in isolated, decapsulated rat glomeruli using <sup>14</sup>C-inulin. The glomerular inulin space significantly decreased when treated with 0.1 n M to 1 µ M of angiotensin II. The decrease was dose-dependent and blocked by 1-Sar, 8-Ile angiotensin II. Since the glomerular intracapillary space seems to occupy the majority of the extracellular (inulin) space in decapsulated glomeruli, these results suggest that angiotensin II decreases the glomerular intracapillary volume. This action of angiotensin II may lead to a reduction in glomerular filtering surface area, and thus, in the ultrafiltration coefficient.