Alpha-synuclein (alphaSN) has been implicated in Parkinson's Disease (PD) and alphaSN is a major component of Lewy bodies (LBs). This study explored platelets as a model system for study of alphaSN metabolism and platelet alphaSN as a diagnostic marker for PD. We used Western blot analysis to characterize and compare platelet and brain alpha-, beta- and gammaSN; and to quantitate alphaSN levels in platelets from PD and age-matched controls. We found that platelets contain full-length alphaSN and 6 and 12 kDa fragments, and gammaSN-like protein. alphaSN and gammaSN were not secreted by thrombin-activated platelets. Furthermore, we also found that the alphaSN and gammaSN levels in sporadic PD patients and age-matched normal controls were not significantly different. This indicates that platelet alphaSN or gammaSN is not a suitable peripheral diagnostic marker for PD. Platelets may be used for study of alphaSN and gammaSN metabolism, and may give some broad insight into the normal functions of alphaSN and gammaSN.