A 9-yr-old female Bornean orangutan (Pongo pygmaeus pygmaeus) presented with a 48-hr history of depression, lethargy, anorexia, and mucoid discharge from the rectum. Clinical, radiographic, and ultrasonographic examination demonstrated the presence of multiple distended loops of intestine, intestinal adhesions, and free gas within the abdomen. During exploratory laparotomy, fibrinopurulent diffuse peritonitis as a result of a ruptured intrapelvic abscess with associated large bowel adhesions was evident. The abdomen was thoroughly lavaged, necrotic debris and abscess wall removed, and fibrinous adhesions disrupted. The orangutan was kept sedated for 48 hr to allow for intensive care. Six months later, when the orangutan presented with similar clinical signs, ultrasonographic examination demonstrated the presence of a pelvic abscess. The previous procedure was repeated with the addition of a hysterectomy. This report is the first documentation of long-term management following surgical intervention for internal abdominal abscessation and septic peritonitis in a great ape.