The authors report a case of deliberate self-poisoning in a drug addict who swallowed elemental mercury: in so doing he inadvertently acquired a permanent diffuse deposition of mercury particles throughout both lung fields. Swallowed mercury should be relatively harmless in small quantity but the high specific gravity and free flowing properties of elemental mercury allowed it to overcome the normal swallowing pathways--such that some of it passed into the bronchial tree instead of passing harmlessly through the gut. In that site its significant vapour pressure, together with its potential for oxidation to inorganic mercury--which may, in turn, be absorbed across the alveolar membrane, gives high potential for mercury poisoning.