Intussusception is the invagination of one bowel segment into another. It is an emergent condition that most commonly affects infants between five and nine months of age, but it can also occur in other age groups. The etiology is usually idiopathic in infants five to nine months of age; neonates, older children and adults more commonly have lead points such as a Meckel's diverticulum or a neoplasm. Early diagnosis is essential to avoid treatment delays, which can increase morbidity and mortality. It has been reported that patients with intussusception present with abdominal pain, vomiting and bloody stools, but this classic triad is often absent. More commonly, lethargy and irritability are the presenting signs. A rectal examination, with testing for occult blood, is an important part of the evaluation and is frequently positive. Barium enema is the gold standard for diagnosis and also has therapeutic potential for reducing the intussusception. Ultrasound is an accurate, low-risk screening tool when performed and interpreted by an experienced ultrasonographer. Surgical reduction is performed if nonoperative reduction is contraindicated or unsuccessful, or if a lead point is suspected.