To determine the effect of moderate doses of ethanol on lipoprotein metabolism, the kinetics of [125I]high density apolipoprotein (Apo) A-I and [131I]low density Apo B were examined in 9 normal volunteers before and after regular intake of 60-70 g of ethanol/day. Plasma levels of Apo B and Apo A-I were significantly increased but remained in the normal range. Mean synthesis of Apo A-I and B were increased, respectively, from 12.6 and 13.7 mg/kg per day in the absence of ethanol to 18.8 and 17.1 mg/kg/day after 2 wk of ethanol intake. Fractional catabolic rates for Apo A-I and B increased respectively from 0.204 and 0.340 in the period without ethanol to 0.266 and 0.372 after ethanol. These findings indicate that despite rather moderate increase in both Apo plasma levels, ethanol produced profound alterations in their metabolism, namely increased turnovers.