NMR methods are being applied to study phospholipid metabolism of cancer cells by monitoring the resonances which appear in the 31P spectrum. This review, aside from considering the applicability of NMR to this specific pathway, raises the question of whether the phospholipid metabolite peaks observed by MR are indicators of cancer cell function or tumor response to treatment. After assessing the results from many investigations, it is concluded that there is no clear correlation and that a combination of techniques, including in vitro and extract studies, will be necessary for a more comprehensive evaluation of the in vivo data.