The results of a series of experiments in the cold-preserved rat liver, applying a newly developed method of pretransplant viability testing, are described. The livers were stored either under simple hypothermic conditions (KHB) or in EC, HTK, or UW preservation solution. Livers were stored up to 48 hr and reperfused after a period of hypothermic storage of 1, 7, 14, or 21 hr. In a parallel series of experiments, with livers stored under identical conditions, repeated proton relaxometry measurements (0, 1, 7, 14, 24, 32, 48 hr) were undertaken; and ATP, ADP, AMP (Atkinson's energy charge), and water content of livers, as well as pH of storage solution, were estimated. Based on a strong correlation between proton spin-spin relaxation time T2 and tissue water content (edema), this new method may be useful to estimate the amount of cell swelling during hypothermic storage from a surgical biopsy of about 200 mg within a few minutes. There was, however, no significant correlation found between energy charge and/or pH and water content, T2, or bile flow. Our method could be useful as a rapid test method in experimental cold liver storage models and may be of interest in human liver transplantation as a viability indicator in combination with other parameters.