Rare, inherited mutations causing familial forms of Parkinson's disease (PD) have provided much insight into some of the molecular mechanisms that underlie both the genetic and sporadic forms of the disease. The role of mitochondria in sporadic PD has been debated for a little over 20 years, since the identification of complex I deficiency in the substantia nigra pars compacta (SNpc) (1). However, it was the identification of loss-of-function recessive mutations in the PINK1 gene, encoding a mitochondrial, putative protein kinase, that reignited interest in the pathophysiology of mitochondria and their potential role in parkinsonism (PARK6) (2). In Drosophila models of PINK1, it has been shown that PINK1 and parkin (the PARK2 locus) (3) act, at least in part, in a common pathway. These studies strongly suggested a role for PINK1 in normal mitochondrial function and implied that parkin was downstream of PINK1. Nevertheless, the role of PINK1 in mammalian mitochondrial function remained unclear. The role of DJ-1 a third recessive parkinsonism locus (PARK7) (4) is also likely to relate to mitochondrial function (5), although whether it too maps to the same pathway as PINK and parkin is not yet clear. In any event, these genetic data clearly show an important role for the mitochondrion in the recessive parkinsonisms, although the extent to which these findings will be relevant to sporadic PD remains unclear (1, 6).