Hypoxia plays an important role in prognosis and therapy response of cancer. This study explores the characteristics of multi-parametric measurements of relative oxygen extraction fraction (rOEF) in a sample of 36 mostly high grade glioma patients. This study confirms previous results in human glioma where rOEF values were found to increase with tumor grade but does not find a similar increase of a supposedly hypoxic tumor area with tumor grade. According to present results, high rOEF values, supposedly corresponding to a high oxygen extraction, prevail in edematous tissue with low rCBV. Whether this translates into tissue hypoxia, needs further investigation.