A method is proposed for reiterated measurements by turns of13C and15N NMR signals at intact rat liver tissue. Eight minutes after Wistar rats had been injected 1,2-13C;15Nglycine, the liver was excised and stored in the triple resonance probe-head of a 2.1 Tesla NMR spectrometer. Alternatively13C and15N spectra were taken over some hours. Continued enzymatic activities of the liver tissue were seen in terms of metabolic changes of each of the carbon and nitrogen groups of glycine. Different half lives were found for the disappearance of the groups. The measurements gave insights into the kinetics and metabolism of an amino acid as an example to follow the vitality of an isolated organ non-destructively.