The incidence of Parkinson's disease (PD) increases with age. PD is a neurodegenerative disease with an incidence of 1 in 200 individuals aged over 65 years. In patients with PD, α-synuclein may accumulate abnormally and damage cells in the substantia nigra. Abnormal proteins (α-synuclein) in peripheral tissues were recently found to be transferred to the brain rather than originating in the brain. Furthermore, changes in intestinal microbiota appear to be related to observed treatment effects and disease development in patients with PD. This review will report on recent studies of intestinal microbiota potentially involved in PD symptoms and progression.