Neurons in the rostral ventrolateral medulla (RVLM neurons) receive inputs from various sources, including baroreceptors, and then regulate activity of sympathetic preganglionic neurons. Though RVLM neurons are assumed to mediate the viscero-sympathetic reflex, it has not been clarified yet. Here we give a brief overview of the participation of RVLM neurons in the viscero-sympathetic reflex. We conclude that RVLM neurons show excitatory and inhibitory responses to stimulation of sympathetic afferents and mediate multi-phase reflex responses of the sympathetic nerve.