Cerebral metabolic rate of oxygen (CMRO2) is an important marker for brain function and brain health. Existing techniques for quantification of CMRO2 with positron emission tomography (PET) or MRI involve special equipment and/or exogenous agents, and may not be suitable for routine clinical studies. In the present study, a noninvasive method is developed to estimate whole‐brain CMRO2 in humans. This method applies phase‐contrast MRI for quantitative blood flow measurement and T2‐relaxation‐under‐spin‐tagging (TRUST) MRI for venous oxygenation estimation, and uses the Fick principle of arteriovenous difference for the calculation of CMRO2. Whole‐brain averaged CMRO2 values in young, healthy subjects were 132.1 ± 20.0 μmol/100 g/min, in good agreement with literature reports using PET. Various acquisition strategies for phase‐contrast and TRUST MRI were compared, and it was found that nongated phase‐contrast and sagittal sinus (SS) TRUST MRI were able to provide the most efficient and accurate estimation of CMRO2. In addition, blood flow and venous oxygenation were found to be positively correlated across subjects. Owing to the noninvasive nature of this method, it may be a convenient and useful approach for assessment of brain metabolism in brain disorders as well as under various physiologic conditions. Magn Reson Med, 2009. © 2009 Wiley‐Liss, Inc.