['Phosphatidylethanolamine N-methyltransferase participates in the synthesis of membrane phosphatidylcholine. Its activity was reported to be decreased in patients with alcoholic cirrhosis, but it is not known whether this is a consequence of the cirrhosis or precedes it. This question was studied in a baboon model of alcohol-induced fibrosis. Phosphatidylethanolamine N-methyltransferase activity was measured in sequential percutaneous needle liver biopsies by the conversion of phosphatidylethanolamine to phosphatidylcholine, using radioactive S-adenosylmethionine as a methyl donor. Chronic alcohol consumption (1-6 years) significantly decreased hepatic phospholipid and phosphatidylcholine levels and reduced phosphatidyl-ethanolamine N-methyltransferase activity even before the development of fibrosis. These effects were prevented or attenuated by supplementing the diet with 2.8 g/1000 kcal of a preparation rich in dilinoleoyl phosphatidylcholine, a highly bioavailable phosphatidylcholine species. There were significant (p < 0.001) correlations between phosphatidylethanolamine N-methyltransferase activity and both hepatic phosphatidylcholine (r = 0.678) and total phospholipid (r = 0.662).'] Is hepatic phosphatidylethanolamine methyltransferase activity decreased by ethanol and increased by phosphatidylcholine?