Leuprorelin acetate is a synthetic agonist of gonadotropin-releasing hormone(GnRH). Because the long term stimulation with leuprorelin acetate downregulates the gonadotropins, it is used for the treatment of the diseases such as prostate cancer, endometriosis and precocious puberty. Although cutaneous adverse events like erythema, induration, sterile abscess and granulomas due to the leuprorelin acetate injection are occasionally reported, precise etiology and pathology is still debating. Only three cases of cutaneous reactions of leuprorelin acetate were reported in Korea. We report the rare case of localized reaction secondary to leuprorelin acetate injection in precocious puberty. An 8-year-old girl presented with erythematous patch with central induration on buttock and left upper arm. She was on the treatment with monthly leuprorelin injection for the precocious puberty. The location of the lesions was consistent with the previous injection site. The lesions appeared after every period of the injection and persisted for 3 to 4 days. Biopsy was performed under the differential diagnosis of injection site reaction, insect bite and foreign body granuloma. Histopathologic findings showed vasculitis with eosinophilic infiltration on buttock and granulomatous inflammation with scattered eosinophils, lymphocytes and multiple microvacuoles on arm. These findings suggested injection site hypersensitivity to leuprorelin acetate.