Studies of left atrial (LA) function, until the latter part of the 20th century, were mostly limited to experimental animal models and to studies related to clinical research in the cardiac catheterization laboratory. For this reason, LA function has received considerably less attention than left ventricular (LV) functions, even though evidence suggests that LA myopathy and failure may exist as an isolated entity, precede and/or coexist with LV myopathy. The introduction of echocardiography and Doppler echocardiography in clinical practice has contributed significantly to our understanding of LA function and its interrelationships with the LV, aorta, pulmonary artery and other parts of the cardiovascular system. In addition, LA with the secretion of atrial natriuretic peptides is playing an important role in cardiovascular and neurohumoral homeostasis. Today, it is well known that LA structural and functional abnormalities that are present in many diseases and disorders constitute a powerful prognostic indicator. As technology (echocardiography, magnetic resonance imaging, computed tomography and others) continues to evolve, it is expected that, in the near future, LA structure and function will be routinely used as LV function is used today.