With respect to neural control of the heart, intrathoracic ganglia and their interconnections form the final common pathway for autonomic modulation of regional cardiac function. In this review, data are presented indicating that such ganglia that include those distributed on the heart contain afferent (sensory) and efferent (motor) neurons that intercommunicate via local circuit neurons. The intrathoracic reflexes involving these neurons function in a coordinated fashion with central neurons located in the spinal cord, brain stem, and supraspinal central neuronal regions to regulate cardiac output on a beat-to-beat basis. The focus of this review is the putative role that these various populations of intrathoracic neurons play in regulating normal cardiac function and, in particular, how their interactions can become altered following their decentralization or in the presence of altered regional cardiac function. It is proposed that a thorough understanding of the interactions that occur among the hierarchy of neurons within intrinsic cardiac and intrathoracic extracardiac ganglia is required in order to assess cardiac regulation in normal as well as diseased states.