This document provides guidelines for the echocardiographic assessment of abnormalities of the interatrial septum, including atrial septal defects and patent foramen ovale. It outlines imaging protocols and views using transthoracic, transesophageal, and intracardiac echocardiography. Parameters for characterizing normal anatomy and defects are described. The role of echocardiography in evaluating patients for transcatheter closure procedures is covered. Assessment of shunting, chamber size, pulmonary circulation, and post-procedure imaging are addressed.