“Chasing the dragon” is a toxic leukoencephalopathy caused by inhalation of heroin fumes.The term“chasing the dragon”appears to have originated in China in the 1920s and became a popular mechanism of heroin administration in the 1950s in Hong Kong because the drug was cheap but impure.A small quantity of powder is placed on aluminium foil,which is then heated underneath with a lighter or matches.The heroin liquefies into a reddish brown glob, which moves around on the foil and emits a white vapor.The glob or“dragon”is“chased”with the lighter underneath while the vapor is sucked through a straw or pipe.