DJ-1 was initially identified by us as a novel oncogene and has recently been found to be a causative gene for familial Parkinson's disease PARK7. DJ-1 plays roles in transcriptional regulation and in oxidative stress function, and its oxidative state at the cysteine residue 106 (C106) determines activities of DJ-1. Elevated levels of oxidation of DJ-1 were observed in brain tissues of patients with Parkinson's disease (PD) and patients with Alzheimer's disease (AD). In this study, we established specific antibodies using synthetic peptide containing SO(3)H at C106 of DJ-1 as an immunogen. These antibodies were found by Western blot analysis to recognize DJ-1 specifically oxidized at C106 but not at other cysteines. These antibodies should be useful to study pathophysiologies of PD and AD.