Serum from two groups of rabbits, all offspring from the same parents, was subjected to NMR spectroscopy in order to monitor the progress of malignant disease. One group had VX-2 carcinoma implanted in the kidney while the control group were sham-operated with injection of physiological saline. Later, the control group was subjected to dietary restrictions to produce a weight loss equivalent to that of the rabbits with tumor. Progressive cancerous growth with cachexia produced characteristic changes in the lipoprotein spectra distinctly different from those induced by weight loss induced by food intake restrictions. A shoulder on the high-field side of the methylene resonance observed in the control spectra disappeared during the progress of cancerous growth. These spectral changes, however, are not adequately described by line width measurements at half-height as suggested for the original Fossel test.