In cats, brain tissue pressure (BTP) was measured by the wick-catheter method. The BTP was positive, but lower than cerebrospinal fluid pressure. Elevation on central venous pressure led only to a transient proportional increase of BTP. When the calvaria and dura of one hemisphere were removed, the rise of BTP was even less. Water content of the brain was normal in either case, even after prolonged venous hypertension. Venous hypertension led in all cases to a marked increase of the brain volume which was caused by vessel dilatation. In brain edema, produced by rinsing the brain surface with ouabain and concentrated saline, BTP was increased permanently by venous hypertension. The water content of the brain was much greater than normal. From these results it was concluded that congestive edema does not occur in the brain unless the tissue is damaged. However, venous hypertension does cause brain swelling.