The case of a patient who injected 10 cc of metallic mercury subcutaneously into his left forearm through multiple punctures in an attempt at suicide is presented. Diagnosis was made by plain radiography of his left forearm, which exhibited redness, edema, and tenderness on the third day postinjection. Early excision of all affected subcutaneous tissues including metallic mercury deposits was performed on the fifth day postinjection. Blood and urine mercury levels that were initially found in high levels decreased dramatically to normal ranges after the excision and remained unchanged at the follow-up period of 6 months. No renal or hepatic functional impairment was encountered. The patient was free of toxic symptoms and mercury embolism. The local, aseptic lytic property of metallic mercury, which could cause severe damage to vital structures, was observed perioperatively. Early diagnosis and early, massive excision of mercury deposits in affected tissues is the important treatment modality in these rare cases.