¹⁷O spin relaxation times and sensitivity of detection were measured for natural abundance H₂¹⁷O in the rat brain at 4.7 and 9.4 Tesla. The relaxation times were found to be magnetic field independent (T₂ = 3.03 ± 0.08 ms, T = 1.79 ± 0.04 ms, and T₁ = 4.47 ± 0.14 ms at 4.7T (N = 5); T₂ = 3.03 ± 0.09 ms, T = 1.80 ± 0.06 ms, and T₁ = 4.84 ± 0.18 ms at 9.4T (N = 5)), consistent with the concept that the dominant relaxation mechanism is the quadrupolar interaction for this nucleus. The ¹⁷O NMR sensitivity was more than fourfold higher at 9.4T than at 4.7T, for both the rat brain and a sodium chloride solution. With this sensitivity gain, it was possible to obtain localized ¹⁷O spectra with an excellent signal‐to‐noise ratio (SNR) within 15 s of data acquisition despite the relatively low gyromagnetic ratio of this nucleus. Such a 15‐s 2D ¹⁷O‐MRS imaging data set obtained for natural abundance H₂¹⁷O in the rat brain yielded an SNR greater than 40:1 for a ∼16μl voxel. This approach was employed to measure cerebral blood flow using a bolus injection of H₂¹⁷O via one internal carotid artery. These results demonstrate the ability of ¹⁷O‐MRS imaging to reliably map the H₂¹⁷O dynamics in the brain tissue, and its potential for determining tissue blood flow and oxygen consumption rate changes in vivo. Magn Reson Med 45:543–549, 2001. © 2001 Wiley‐Liss, Inc.