Gait and balance disturbances are one of the most incapacitating symptoms of Parkinson's disease (PD) (Boonstra et al. 2008). They can cause falls and are therefore associated with the negative spiral of (near) falls, fear of falling, fractures, reduced mobility and social isolation; hence, having a profound negative impact on quality of life (Lin et al. 2012). Originally, symptoms of PD were ascribed to dopamine deficiency and basal ganglia dysfunction (Wu et al. 2013). However, in the last decades it has become clear that other brain structures are also involved in the pathophysiology of PD (Snijders et al. 2011; Stefani et al. 2007). An intriguing, emerging insight is that the cerebellum may be involved in the pathophysiology of PD (Wu et al. 2013). That is, the cerebellum is hyperactive in PD patients during different motor tasks (Yu et al. 2007; Hanakawa et al. 1999; del Olmo et al. 2006). However, whether cerebellar hyperactivity is pathological or compensatory and how it affects gait and balance in PD patients remain open questions. Here, the investigators aim to elucidate the role of the hyperactive cerebellum in gait dysfunction in PD patients by modulating cerebellar excitability with state-of-the-art non-invasive brain stimulation techniques and investigate the effects on gait.