1. Patients with a history of alcohol abuse were studied by 31P n.m.r. spectroscopy of the liver in vivo, and the results were related to the pattern of disease assessed by standard biochemical and histological techniques. 2. The ratios of metabolites measured from the 31P n.m.r. spectra were abnormal in patients with alcoholic hepatitis but not in those with fatty change or cirrhosis in the absence of hepatitis. In particular, the levels of phosphomonoesters were raised, with respect either to Pi, or to adenosine 5'-triphosphate. The level of phosphomonoesters showed a significant positive correlation with the severity of alcoholic hepatitis, assessed by histology. 3. The ratio of Pi to adenosine 5'-triphosphate was used as a measure of the energy status of the hepatocytes, and was unchanged between patients and controls.