There is gathering evidence that Hb levels within the brain affect the risk of developing neurodegenerative diseases including PD.11–15 Reports associate Hb and neuronal Hb levels with Alzheimer’s disease, dementia with Lewy bodies, age-associated cognitive decline, and argyrophilic grain disease.10 We postulate here that Hb has an intraneuronal role in contributing to the changes in oxidative status and mitochondrial dysfunction that have been associated with PD. This evidence concerns the gene GSTM1 and early-onset autosomal dominant Alzheimer disease.