From a foundation stock of HS/Ibg mice, mass selection has yielded high-ethanol acceptance (HEA) and low-ethanol acceptance (LEA) lines with distributions which show little overlap in the 10th generation. Divergence has been systematic and the estimate of the realized heritability after 10 generations of selective breeding is 0.21 +/- 0.04. Low to moderate correlations among three methods of measuring alcohol consumption, including the one on which selection was based, were shown in an F2 generation derived from C57BL/Ibg and C3H/Ibg mice.