Ethanol interacts with several central transmission systems. Following ethanol application we observed an inhibition of locomotion, vigilance and muscle tone in a modified Irwin-behaviour test. The effect was strengthened by a single dose of haloperidol. Contrary to this observation the ethanol effects decreased when haloperidol was given repeatedly for weeks before the application of ethanol. Three days after haloperidol withdrawal in case of nearly complete haloperidol elimination and development of dopaminergic supersensitivity the decrease was most pronounced. The results indicate that ethanol effects on dopaminergic functions are weakened in consequence of an increased efficiency of the adequate transmission system and vice versa.