A 20-year-old laborer developed moderate parkinsonism 1 week after accidentally ingesting a petroleum waste mixture. Parkinsonism persisted for 3 months and then began to improve, although subtle signs remained 29 months after exposure. 6-Fluorodopa-labeled positron emission tomography (6-FD PET) performed 3 months postexposure revealed a striatal dopamine rate constant level of 0.170 ml/striatum/min, nearly 3 SD below the mean for age-matched controls. However, subsequent PETs demonstrated 6-FD PET rate constants not significantly different than controls. Although the causative agent has not yet been identified, this case suggests that compounds capable of causing parkinsonism may exist in commonly used petroleum products.