A large body of experimental evidence supports a role for oxidative stress as a mediator of nerve cell death in Parkinson-s disease (PD). Phytoestrogens such as genistein have been reported to prevent neuronal degeneration caused by increased oxidative burden, therefore, this study examined whether genistein administration at a high dose would attenuate behavioral and structural abnormalities in an experimental model of PD in rat. For this purpose, unilateral intrastriatal 6-hydroxydopamine (6-OHDA, 12.5 μg/5 μL of saline-ascorbate)- lesioned rats were intraperitoneally pretreated with a single and high dose of genistein (10 mg/kg) 1 h before surgery. Apomorphine-induced rotations and the number of Nissl-stained neurons in the substantia nigra pars compacta (SNC) were counted after 2 weeks. Genistein administration could attenuate the rotational behavior in lesioned rats and protect the neurons of SNC against 6-OHDA toxicity. Genistein administration has a protective effect against 6-OHDA toxicity.