The heart is richly innervated with sympathetic and parasympathetic fibers that work in conjunction with norepinephrine to accurately preserve hemodynamic and electrophysiological stability at rest and during periods of increased cardiovascular demand. Imaging of the cardiac sympathetic system is an area of active investigation in a wide variety of conditions, such as heart failure, arrhythmias, and ischemic heart diseases, providing an independent ability to risk stratify and a potential guide for improving patient management. 123 I-metaiodobenzylguanidine (MIBG), an analog of the false neurotransmitter guanethidine, represents the most widely studied tracer for imaging of the cardiac autonomic system. Myocardial scintigraphy with 123 I-MIBG is widely used in Europe and Japan but to date there is no established standard for tracer administration, imaging acquisition, and interpretation. We discuss the current literature regarding methods and interpretation of 123 I-MIBG cardiac innervation imaging.