While problems of resolution and sensitivity still persist, it is now possible to perform magnetic resonance spectroscopy on a number of human tumors. Experiments to date on human brain tumors demonstrate the potential of proton, phosphorous, and sodium magnetic resonance spectroscopy for the evaluation of tumors with respect to their biology, metabolism, and response to treatment. Depending on the differences between normal and neoplastic spectra, similar results may pertain to tumors in other organs. Multi-institutional studies are required because of the small numbers of tumors available to individual laboratories.