1. Glomerular filtration rate was determined from 51Cr—EDTA clearance in twenty hypertensive subjects treated with propranolol.
2. A significant mean decrease of 13% in the glomerular filtration rate was found during treatment, and an increase of the same order of magnitude after withdrawal of propranolol.
3. It is suggested that these changes are related to a reduction in the renal blood flow.
4. No significant changes were found in plasma volume.