Clinical proteomics is a powerful tool that can be used to identify proteins that are differentially expressed in disease states, leading to greater understanding of the molecular and cellular events that contribute to disease. The aim of this study was to identify protein changes in the sera from Chinese Parkinson's disease (PD) patients, with the goal of finding biomarkers for PD diagnosis, and to elucidate the events occurring at the onset of PD. Using differential display to identify proteins with altered expression in PD patients, we obtained 15 protein spots corresponding to 13 different gene products that were likely to be involved in PD. Two-dimensional gel electrophoresis and mass spectrometry were used to identify differentially expressed proteins, 7 of which have never previously been associated with PD patients. They are likely to be involved in antioxidation, lipid metabolism, intracellular transport, cell proliferation and immunoregulation. The altered levels of these proteins may be related to the pathophysiological mechanisms of PD. As a result, some of these proteins could be considered as candidate biomarkers.