Results of previous studies on the effects of ethanol consumption for a single fixed period on the properties of D2 dopamine receptors appear contradictory and inconclusive. In this study, we have examined the time course of the effects of dietary ethanol on the properties of striatal D2 dopamine receptor. Ethanol intake led to a significant decrease in the maximum number (Bmax) after 1 (35% of control) and 2 weeks (48% of control), but not after 3 (93% of control) or 4 weeks (97% of control) of treatment. However, there was a significant increase in Bmax after 6 (118% of control) and 10 weeks (123% of control) of ethanol consumption. The affinity (Kd) of the receptor, however, remained unaltered in all cases. In conclusion, these data show that the duration of ethanol exposure may be an important determinant regulating D2-dopamine receptor density.