A case-control study showed that, compared with infants who had never been fed human milk, breast-fed infants had a relative risk of intussusception of 6.0 (95% confidence interval, 1.8 to 20.4) when breast-feeding at admission was exclusive and of 2.3 (95% confidence interval, 0.8 to 6.6) when it was partial. Exclusive breast-feeding may be a risk factor for intussusception in infancy.