The pathologic hallmark of Parkinson's disease is the dopaminergic cell death in the substantia nigra (SN). The cause of the cell death is, however, unknown. Even the question on whether the cells die by apoptosis or necrosis has not been answered with certainty. In 6-Hydroxydopamine induced Parkinsonian rats, the present study observed apoptotic nuclei from 1 day to 14 days after lesioning, using the TdT(terminal deoxynucleotidyl transferase)-mediated dUTP-biotin nick-end labeling method. Tyrosine hydroxylase immunohistochemistry and haematoxylin staining further revealed that these apoptotic cells are dopaminergic cells in the substantia nigra. The results suggest that dopaminergic cells in SN undergo apoptosis in the rat model of Parkinson's disease.