High resolution 31P nuclear magnetic resonance (NMR) was used to evaluate the severity of acute pancreatitis in rats. Experimental pancreatitis was induced by intraparenchymal injection of 10% sodium taurocholate. Pancreases were removed at various time periods and the NMR spectrum of the whole organ was recorded. Metabolic changes taking place during the progression of the disease were measured and correlated with the pathologic changes. Gradual depletion of the high energy compounds, adenosine triphosphate and phosphocreatine, was observed. The NMR spectral changes paralleled the extension of the pathologic lesions and were found to constitute a reliable indicator of the severity of acute pancreatitis. It is suggested that high resolution NMR may be used to evaluate the pathogenesis and therapy of various forms of experimental pancreatitis.