Nine young, healthy male volunteers were given ethanol (75 g/day) for 5 weeks. The ethanol was divided into five daily doses and taken so that blood ethanol levels never exceeded 0.04% (w/v). During the latter part of the ethanol intake period, there was a significant, transient increase of plasma triglyceride (TG) concentrations followed by reduction to normal levels. A three-fold increase of lipoprotein lipase activity (LLA) occurred in biopsy specimens of adipose tissue. An increase of alpha-lipoprotein concentrations, which correlated significantly with the decrease in plasma TG levels and the increase in adipose LLA, was also observed during the ethanol intake period. No changes were observed in plasma cholesterol and beta-lipoprotein levels. A transient, three-fold increase of TG concentrations occurred in liver biopsy specimens. Ultrastructural and cytochemical examinations of the biopsy specimens showed hyperplasia of the smooth endoplasmic reticulum, and increased canallicular activity of gamma-glutamyl transferase (gamma-GT) activity in most subjects towards the end of and after the ethanol intake period. Serum gamma-GT levels also increased significantly.