A 28-year-old man at high risk of mercury vapor exposure, having worked in a lamp factory for 5 years, was recruited to the hospital for a neurologic evaluation. This experimental study obtained both the approval of Institutional Review Board and the worker's informed consent. The worker had complained of memory impairment, palpitations. and depression after working in the factory. His biologic urine mercury level was 9.18 mu g/g creatinine. There was no abnormality oil the brain-CT scan. However, imaging with Tc-99m TRODAT. an agent for dopamine transporter and measuring dopamine innervation of the striatum, showed markedly decreased uptake in bilateral striata especially in the putamen. Based oil the worker's occupational history of mercury exposure and biologic Urine mercury level, mercury exposure was confirmed.