It has been reported that the nucleus tractus solitarius affects cardiovascular function in response to baroreceptor stimulation by stimulating the parasympathetic nervous system and by inhibition of the sympathetic nervous system. Experiments reported here have demonstrated that the nucleus tractus solitarius projects to the rostral ventrolateral medulla, and specifically to the immunocytochemically identified adrenergic neurons of the Cl group, which in turn project to the spinal cord. The termination of the aortic depressor nerve in the nucleus tractus solitarius, and the projections of the nucleus tractus solitarius to the ventrolateral medulla, demonstrate a simple pathway by which the baroreflex can influence sympathetic output to the heart and blood vessels. Other experiments reported here have shown projections from the nucleus tractus solitarius to the nucleus ambiguus and surrounding ventrolateral medulla, a region known to be the location of the preganglionic vagal efferent neurons that play a role in regulation of cardiovascular function. This completes the anatomical substrate through which barostimulation can activate parasympathetic cardioinhibition. In addition, these experiments have revealed that in the region of the nucleus ambiguus and surrounding ventrolateral medulla there are cells that project not only through the vagus but also to the spinal cord. Therefore an anatomical substrate has been demonstrated that could subserve baroreflex inhibition of the sympathetic nervous system via a second pathway arising from the dorsal vagal complex.