Some biological characteristics of cancer cells and solid tumors are identifiable by the high resolution NMR relaxation behavior of their nonaqueous components. Chemical analysis and two-dimensional scalar correlated (COSY) NMR spectroscopy show these resonances arise from neutral lipid in the plasma membrane. Triglyceride is shown to be the main plasma membrane component giving rise to the NMR spectrum, while soluble nonmembrane components account for 90% of the remaining resonances in the spectrum of intact cells. The presence of triglyceride has been detected by chemical analysis in highly purified plasma membranes from two different cell lines. The COSY spectra of cancer cells are comparable with that obtained for the triglyceride-rich very low density human lipoprotein.