The cause of Parkinson's disease (PD) is currently unknown. Although a genetic cause has been implicated in familial PD, the vast majority of cases are considered idiopathic. Environmental toxins have been implicated as a cause for PD by many investigators. Unfortunately, the magnitude of this exposure would likely need to be very high and as a result, would likely have been identified by the many epidemiological studies performed to date. Recently, we inadvertently realized that exposure to neurotoxins while still in utero may also represent a risk factor. Thus, exposure to the bacteriotoxin, lipopolysaccharide (LPS) during a critical developmental window in rats, leads to the birth of animals with fewer than normal dopamine (DA) neurons. This DA neuron loss is apparently permanent as it is still present in 16 months old animals (the longest period studied to date). Moreover, the loss of DA neurons seen in these animals increases with age thereby mimicking the progressive pattern of cell loss seen in human PD. The DA neuron loss is accompanied by reductions in striatal DA, increases in DA activity, and increased production of the pro-inflammatory cytokine Tumor Necrosis Factor alpha (TNF-alpha). These are also characteristics of the PD brain. This model therefore shares many of the same characteristics with PD, and most importantly exhibits a slow, protracted loss of DA neurons – a characteristics of this animal model not found in other models. Interestingly, a common complication of pregnancy is a condition known as bacterial vaginosis (BV), which is known to produce increased levels of LPS and pro-inflammatory cytokines in the chorioamniotic environment of the fetus. This raises the interesting possibility that BV may be a risk factor for PD. The possibility that prenatal toxin exposure may contribute to the development of a neurodegenerative disease of the aged raises interesting new pathogenic questions and draws attention to the possibility that in utero exposure to neurotoxins may represent a here to fore unrecognized cause of PD.