Results of previous studies on the effects of ethanol consumption on the properties of D1 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 D1 dopamine receptors. Chronic ethanol intake led to bidirectional changes in the maximum number (Bmax) of [3H]SCH-23390 binding to striatal D1 dopamine receptors measured 10 hrs after termination of the ethanol intake. A significant decrease (80% of control), increase (159% of control), increase (122% of control), and decrease (85% of control) after 1, 2, 3, and 4 weeks of ethanol intake respectively was observed. The bidirectional changes disappeared after 6 and 10 weeks of continued ethanol intake and the Bmax returned back to the control level. The receptor affinity (Kd), however, remained unaltered in all cases. These data suggest that the duration of ethanol exposure may be an important determinant in regulating D1 dopamine receptor density.