The impact of one ventricle on the adjacent ventricle plays a key role in cardiac function. Ventricular-ventricular interactions are based on the arrangement in-series of the circulation and common pericardium, interventricular septum, and myocardial tracts. Imaging, in particular echocardiography, plays a central role in characterizing these interactions through geometric indices, septal configuration and motion, Doppler flow, timing of events in the ventricles and alterations in strain, remodeling, and diastolic filling with altered loading of the contralateral ventricle. Although standard echocardiography techniques are usually adequate to image ventricular-ventricular interactions, recent developments in automation, post-processing, and advanced techniques (e.g., 3-dimensional) could improve detection and understanding of interventricular interactions. Imaging findings must be analyzed in the context of the pathophysiology to correctly assess and understand ventricular-ventricular interactions. This paper reviews the imaging of ventricular-ventricular interactions in acquired and congenital heart disease, demonstrating their importance in a wide array of conditions. (c) 2018 by the American College of Cardiology Foundation.