We reported previously that phosphorylation by casein kinase II (CKII) regulates the interaction between alpha-synuclein and its binding partner synphilin-1, and that both CKII alpha and beta subunits co-localize with alpha-synuclein in cytoplasmic inclusions in transfected cells. In this study, we extended these observations to the brains of patients with Parkinson's disease (PD) and examined whether CKII subunits are present in Lewy bodies. Immunohistochemical studies on PD brains harboring Lewy bodies revealed a positive stain for CKII beta but not for CKII alpha. In addition, CKII beta subunits co-localized with alpha-synuclein in most Lewy bodies. These findings suggest that CKII beta subunits may play a role in the formation of intracytoplasmic inclusions in human alpha-synucleinopathies either through phosphorylation events or through a separate mechanism linked to the beta subunit itself.