Rib notching following various congenital or acquired cardiovascular diseases is discussed in connection with its causes and diagnostic implication on the basis of our own cases and reported cases in the literature. This sign was widely accepted as pathognomonic of coarctation of the aorta, but it occurs in various conditions as the authors point out in this report. Moreover, it is revealed that rib notching may be a result from the markedly augmented intercostal-bronchial collateral circulation as a compensation for the decreased effective pulmonary flow due to a large amount of the right to left shunt, if the adhesion in the pleural space would be present in some congenital malformations with decreased pulmonary blood flow and relative old-aged Morbus caeruleus. This finding is considered an important reference on determining the surgical indication in these conditions in regard to the cause, location and degree of rib notching.