A 51-year-old type 2 diabetic patient with a scrotal subcutaneous abscess is reported. He was diagnosed as having diabetes mellitus five years earlier. Hehad left scrotal swelling and pain with granulocytosis, elevated C-reactive protein and hyperglycemia. He was successfully treated with incision and drainage {Streptococcus agalactiae was identified in the pus), debridement, antibiotics, immunoglobulin and insulin. This case resembled Founder's gangrene, an infective necrotizing fasciitis of the perineal, genital or perianal regions. Diabetes mellitus is a basic disorder often associated with Founder's gangrene. Scrotal subcutaneous abscess should be prevented from progressing to Founder's gangrene with early and appropriate treatment. (Internal Medicine 39: 991-993, 2000)