C57BL mice normally show a preference for alcohol solutions compared with water. The effect of chronic ethanol treatment sufficient to produce behavioural tolerance on the voluntary ethanol consumption of C57BL mice was compared with the effect of acute ethanol and acute and chronic administration of acetaldehyde. Chronic treatment with ethanol caused a loss of preference which lasted more than 12 weeks after withdrawal from the treatment. The acute ethanol treatment and the acute and chronic acetaldehyde treatments only produced a transient loss of preference which returned to normal within 1 week of cessation of treatment. The effect of these drugs on liver alcohol dehydrogenase (LAdH) was also examined. Changes in LAdH activity did not correlate with alcohol preference. Possible reasons for the different effects of the drug treatments on alcohol preference are discussed.