The present study examined the characteristics of behavior Induced by dopamine agonists following treatment with 6-hydroxydopamine(6-OHDA) unilaterally into left striatum in rats. 6-OHDA was administered at doses of 8,16 and 24 $mu extrm{g}$/$mu extrm{l}$(in 0.1% ascorbic acid) into dopaminergic neurons in left striatum of 7 weeks old rat under anesthetic. Locomotor activity was significantly decreased at 1 week following 6-OHDA-administration in 7 weeks old rats. The contralateral circling behavior was induced by apomorphine(5 mg/kg, i.v.) after 1 week following 6-OHDA(24$mu extrm{g}$/$mu extrm{l}$) treatment, and was further increased by repeated administration of apomorphine at 2, 3 and 4 weeks. The contralateral circling behavior was also induced by lisuride and 1-dopa in a dose dependent manner, but not by SK & F 82526 in 7 weeks old rats treated with 6-OHDA. The contralateral circling behavior was significantly higher in 21 weeks old rats but significantly lower In 35 weeks old rats when compared with 7 weeks old rats. The contralateral circling behavior induced by apomorphlne did not differ significantly in 7 and 35 weeks old male and female rats. These results suggest that 6-OHDA treatment into left striatum causes remarkable destrurtion of intrastriatal dopaminergic netcons leading to dopaminergic receptor supersensitivity. Thus, the contralateral circling behavior in duces by apomorphine may be used as indicator for neurodegenerative diseases.