Labeled leucine can be used to measure accurately the rate of both total and secretory protein synthesis by isolated hepatocytes if at least 1 mM leucine is added to the incubation medium, even in the presence of 50 mM ethanol. Using this technique it was found that ethanol caused a significant inhibition of very low density lipoprotein (VLDL) as well as total protein synthetic rates in hepatocytes from both fed and fasted rats. In contrast, a single acute oral dose of ethanol to fasted rats caused within 4 hr a threefold stimulation in the rate of VLDL synthesis without affecting the total protein synthetic rate in the hepatocyte system.