We review the recent progress in the research of the etiology, pathogenesis and treatment of Parkinson's disease. It has been postulated that mitochondrial respiratory failure and oxidative stress are two major contributors to nigral cell death in Parkinson's disease. Loss of mitochondrial complex I and the alpha-ketoglutarate dehydrogenase complex in the substantia nigra has been reported. Evidence to indicate oxidative stress includes a high dopamine content, increase in superoxide dismutase activities, increase in iron, and decrease in glutathione in the substantia nigra. The question posed is which one occurs first. We believe mitochondrial respiratory failure occurs first, because slowing down of the electron transport induces an increase in the formation of activated oxygen species. The primary cause of Parkinson's disease is still unknown, but we believe the interaction of environmental toxins and genetic predispositions is important. In this respect, molecular genetic studies on familial Parkinson's disease are very important.