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Human erythrocytes were incubated with heat-inactivated plasma, and the transfer of cholesterol to the red cells was followed to equilibrium over 24 hr. When cholesterol-enriched plasma was used, there was a net flow of sterol into red cells. Ethanol, in a concentration-related manner, accelerated the cholesterol transfer without appreciably affecting the final sterol content of the erythrocytes at equilibrium. Ethanol also accelerated the exchange of tritiated cholesterol between normal or cholesterol-enriched plasma and red cells, whether or not there was a net cholesterol flow. Ethanol speeded up sterol transfer from several cholesterol donors, including prelabeled erythrocytes, low-density lipoproteins, high-density lipoproteins, and egg lecithin vesicles. Ethanol (0.35 M) increased the rate constant of the transfer by about 30-40% with different sterol donors. These observations may be related to the previously reported increase in cholesterol in the brain and red cell membranes of mice after chronic treatment with ethanol.