Rib notching was detected in 20 of 55 children with known coarctation of the aorta. Notching occurred in 15% of 33 patients under one year of age and in 68% of 22 patients between one and seven years of age at time of diagnosis. Rib erosions in infants and young children are easily overlooked due to minor involvement of only one or a few ribs. The frequency of rib notching is shown to increase with increasing pressure gradient across the coarctation.