It is now recognized that the cell-to-cell transmission of misfolded proteins such as α-synuclein contributes to the neurodegenerative phenotype in neurological disorders such as idiopathic Parkinson's disease, Dementia with Lewy bodies, and Parkinson's disease dementia. Thus, establishing cell-based models for the transmission of α-synuclein is of importance to understand the mechanisms of neurodegeneration in these disorders and to develop new therapies. Here we describe methods to study the neuron-to-neuron propagation of α-synuclein in an in vitro setting that also has in vivo applications.