RATIONALE AND OBJECTIVES. The authors describe the clinical status of liver tissue with only a single numerical quantity (total entropy) derived from spectroscopic data of 31P-magnetic resonance (MR) spectra. METHODS. Twenty-four patients with liver metastases and 20 volunteers were investigated with image-guided volume selective 31P-MR spectroscopy on a 1.5-T whole body scanner. From each in vivo 31P-MR spectrum, the ratios of phosphomonoester (PME)/β-adenosine triphosphate (ATP), inorganic phosphate (Pi)/β-ATP and phosphodiester (PDE)/β-ATP and the total entropy (H*) were calculated. Mean values and standard deviations were determined and significance of the differences were tested with Student's t test. RESULTS. For patients, the H* = 4.7 ± 4.3, PME/β-ATP = 0.72 ± 0.28, Pi/β-ATP = 1.00 ± 0.39, PDE/β-ATP = 1.68 ± 0.59. For the volunteers, H* = 7.6 + 2.5, PME/β-ATP = 0.39 + 0.15, Pi/β-ATP = 0.90 ± 0.19, PDE/β-ATP = 1.25 ± 0.28. The total entropy of patients' spectra showed significantly lower values compared with those of volunteers. PME/β-ATP and PDE/β-ATP of the patients increased and differed significantly from volunteer data. CONCLUSIONS. It was demonstrated that the results of in vivo 31P-MR spectroscopy may be described with a single criterion by means of the total entropy.