Objective: Central application of glucagon-like peptide 1 (GLP-1) inhibits food intake and reduces blood glucose levels. Activation of central GLP-1 receptors also increases blood pressure and heart rate. These results suggest that central GLP-1 neurons modulate sympathetic and vagal outflow. To test this hypothesis, we analysed the projections of preproglucagon (PPG) neurons, which make GLP-1 and were tagged with YFP, to key CNS sites involved in autonomic control. Methods: Transverse sections from transgenic mice expressing YFP under PPG promoter control were revealed with an anti-GFP antibody and avidin-biotin-peroxidase. The distribution of immunoreactive perikarya and fibres was assessed from the anterior commissure to the spinomedullary junction. Results: YFP- immunoreactivity was intense and axons were clearly visible. Most PPG cell bodies were located in the caudal brainstem within the nucleus tractus solitarius (NTS). Fewer somata were found in the intermediate reticular nucleus, and some at the ventral border of the hypoglossal nucleus and in the raphe obscurus. The caudal NTS contained a dense network of dendrites, some of which extended into the area postrema (AP). Immunoreactive axons were widespread throughout NTS, dorsal vagal nucleus and reticular nucleus (except for the parvicellular section) but more limited within the hypoglossal nucleus and the pyramids. The AP, rostral ventrolateral medulla, pontine central grey, parabrachial nucleus and locus coeruleus were moderately innervated and some axons occurred in the amygdala. As in rat, there was heavy innervation of dorsomedial and paraventricular hypothalamus, periaqueductal grey and the paraventricular nucleus of the thalamus. Conclusion: These results demonstrate that PPG neurons project more widely than previously described and innervate primarily brain regions involved in autonomic control. Hence, central PPG neurons are in a prime position to modulate sympathetic and parasympathetic outflow.