We describe a case of pulmonary emboli due to mercury in a female drug addict who was HIV positive and had voluntarily injected herself with mercury. The diagnosis was guided by the history and by the characteristics of the chest radiograph and was confirmed by blood and urine levels of mercury and the radiograph taken of the site of the intravenous injection. Three years after the injection the patient did not reveal any signs suggesting disturbance due to the chronic pulmonary exposure to mercury, but there was a reduced carbon monoxide transfer, whose interpretation was difficult due to the past respiratory history and to the drug addiction.