Dilated cardiomyopathy (DCM) is best understood as the final common response of myocardium to diverse genetic and environmental insults. A rigorous work-up can exclude alternative causes of left ventricular (LV) dilation and dysfunction, identify etiologies that may respond to specific treatments, and guide family screening. A significant proportion of DCM cases have an underlying genetic or inflammatory basis. Measurement of LV size and ejection fraction remain central to diagnosis, risk stratification, and treatment, but other aspects of cardiac remodeling inform prognosis and carry therapeutic implications. Assessment of myocardial fibrosis predicts both risk of sudden cardiac death and likelihood of LV functional recovery, and has significant potential to guide patient selection for cardioverter-defibrillator implantation. Detailed mitral valve assessment is likely to assume increasing importance with the emergence of percutaneous interventions for functional mitral regurgitation. Detection of pre-clinical DCM could substantially reduce morbidity and mortality by allowing early instigation of cardioprotective therapy.