We report 2 cases of necrotizing fasciitis of the perineum, perianal area, and male genitalia (Fournier's gangrene) that arose secondary to intra-abdominal infectious processes (ruptured appendicitis and diverticulitis). Management consisted of immediate debridement of necrotic tissue, exploratory laparotomy, and diverting colostomy. The presence of an acute abdominal process was not immediately evident on initial evaluation of either patient. This demonstrates the critical importance of considering intra-abdominal infection in patients with Fournier's gangrene when the more commonly seen urinary tract, perirectal, and traumatic causes are not readily apparent.