Pyridine nucleotide fluorescence in perfused rat liver for the noninvasive determination of donor graft viability was investigated in relation to other metabolic indices, such as NAD concentration, adenine nucleotides, and mitochondrial phosphorylative activity. The amplitude between oxidation and reduction levels (R×A) in fluorometric trace, and the slope or the velocity of the trace curve from oxidation to reduction (R×V) were determined by the measurement of fluorescence from NAD(P)H, using a new fluorometric device, R×A and R×V decreased proportionally to the duration of preservation period (6, 12, 24, 48 hr) in simple cold storage. Other values of hepatic cell viability, such as total adenine nucleotides, energy charge, and mitochondrial phosphorylation rate, were simultaneously measured and also decreased proportionally to the duration of preservation period. There were close positive correlations between the percentage of R×A and NAD concentration (r=0.724,p<0.01), between the percentage of R×A and total adenine nucleotides (r=0.887,p<0.01), between the percentage of R×V and energy charge (r=0.715,p<0.01), and between the percentage of R×V and phosphorylation rate/cytochrome a(+a3) (r=0.837,p<0.01). These results suggest that this fluorometric method can provide an accurate noninvasive evaluation of donor graft viability—and, unlike the present indices of energy metabolism, it may be applied to evaluate the primary nonfunctioning graft prior to transplantation.