The cardiac conducting system is vital for generating and synchronizing the heartbeat. Beginning with Tawara, Einthoven and other pioneering workers, a wealth of information has been collected over the last 100 years on the histologic, morphologic and physiologic characteristics of specialized cardiac tissues. However, in the last ten years considerable effort has been put into understanding the cellular and molecular mechanisms governing its development. During this latter period, controversies have also arisen as to the nature of the signaling mechanisms involved in induction and patterning of the conducting system, particularly with respect to the pathways functioning in mammals. In this review, we will try to summarize the current state of knowledge in this field and point out some of the remaining questions.

        Key words: cardiac conduction system, heart, development, endothelin