Parkinson's disease(PD) is a neurodegenerative disorder characterised clinically by bradykinesia, rigidity, tremor, and pathologically by neuronal cell death in substantia nigra. The cause of dopaminergic neuronal cell death in PD remains unknown. Recently, decreased mitochondrial complex I activities have been reported in platelets, muscles, substantia nigra of the PD patients. Blood samples were lysed with lysis buffer, and incubated 1 hour with 20mg/ml proteinase K at 37degreesC. DNA was extracted with phenol and chloroform(1: ). The long and accurate polymerase chain reaction(LA PCR) was performed by mitochondrial specific primers. The mitochondrial ND1, ND2, CO I, CO II and 1/3ATPase 6/8, CO III, genes as well as parts of ND3 and 3/4ND5 subunit coding regions were analysed by LA PCR. In this study, it is observed not only 4,977 bp mtDNA deletion but a partial mtDNA deletion of the ND1, ND2, CO I~III genes in blood from patients with PD. The result of this study cannot rule out the possibility of point mutation. It is possible that such a deletion would cause mitochondrial dysfuncton, and as a result of mitochondrial dysfunction, Parkinson's disease could progress.