A 20-year-old male was admitted to our hospital with the chief complaints of high fever and pain around his right hip joint. He had his right knee injured with a slight abrasion three weeks before. The diagnosis of suppurative lymphadenitis of inguen was made, and intravenous cefotiam was started. Despite these treatments his fever continued, general edema and dry cough appeared. Arterial blood gas showed severe hypoxia and chest X ray revealed marked cardiomegaly associated with ground-glass opacity over bilateral lower pulmonary fields. Slight renal insufficiency was also observed. On the fifth hospital day, the culture specimens of both blood and pus from the abrasion on admission yielded Streptococcus pyogenes. His condition was diagnosed as severe group A Streptococcus infection, then antibiotics were switched to intravenous administration of high dose aminobenzyl penicillin and clindamycin in combination with protease inhibitor, urinastatin. After these treatments, his condition improved and he was discharged from the hospital after one month. Group A Streptococcus may cause uncommon but life-threatening infection such as septicemia. Early recognition of the disease and prompt initiation of appropriate treatment may lead to successful outcome.