Alcoholic patients often have impaired immune function, yet little is known about the precise mechanism(s) of this impairment. We have previously shown that ethanol consumption by mice alters copolymer‐specific humoral and cellular immune responses. In this study, we asked whether alcohol consumption by mice would phenotypically alter lymphocyte populations. Female C57BL/6 mice were fed a nutritionally complete liquid diet containing 35% ethanol‐derived calories for up to 8 days. As controls, mice either were fed a liquid control diet that isocalorically substitutes sucrose for ethanol or remained on a standard solid diet and water ad libitum. Although mice fed ethanol‐containing liquid or pair‐fed control liquid diets have decreased numbers of spleen cells compared with solid diet controls, only the ethanol‐containing diet allowed normally nonresponder C57BL/6 spleen cells to make antibody responses to the poly(Glu50Tyr50) synthetic copolymer antigen. Flow cytometric analysis of splenic lymphocyte populations of mice on the ethanol‐containing diet shows an increase in the relative proportion of T‐lymphocytes as compared with mice on either solid or liquid control diets. No such change is seen for either B‐cell or natural killer cell populations in these same mice. Both liquid control and liquid ethanol diets caused a slight decrease in the CD4:CD8 ratios of splenic T‐lymphocytes. We see the relative percentage of T‐cells bearing theαβ‐cell receptor (TcR) increases in the spleens of liquid ethanol diet mice; a smaller increase TcRαβusage is seen in the spleens of liquid control mice, compared with solid diet mice. Flow cytometric analysis shows that little, if any, difference exists in TcRγδexpression between the liquid ethanol and either the liquid control or solid diet groups. Preliminary analysis of TcRαβsubsets suggest that ethanol increases the percentage of T‐cells expressing Vβ5 and Vβ8, and decreases the percentage of Vβ11 expressing cells. These findings suggest that, in addition to modifying the immune response, ethanol alters the phenotypi