The atypical parkinsonian syndromes—dementia with lewy bodies, multiple system atrophy, progressive supranuclear palsy, and corticobasal ganglionic degeneration—are often difficult to differentiate from parkinson’s disease and each other. Although these syndromes are clinically distinct, modern immunocytochemical techniques and new genetic findings have revealed intriguing interconnections at a basic molecular level, providing a scientific rationale for lumping these diseases into two groups, the synucleinopathies and the tauopathies.