Paraquat (1,1apos;-dimethyl-4,4apos;-bipyridilium dichloride; PQ) is an effective and widely used herbicide in Asiatic and American countries with a claimed safety record when appropriately applied to eliminate weeds. However, over the last decades a growing body of epidemiologic evidence has been linking longterm/low-dose PQ exposure to the development of Parkinsonâ s disease (PD). PQ is well known for its ability to induce oxidative stress, mitochondrial dysfunction, α-synuclein fibrillation and neuronal cell loss. More recently, more attention has been given to the role of autophagy in several major neurodegenerative diseases and the influence of environmental toxins in this pathway. This chapter provides an overview of the main mechanisms of neurotoxicity of PQ with an emphasis in the autophagic process and its possible relationship to PD. © Springer International Publishing Switzerland 2015.