In a relatively short period of time two-dimensional echocardiography has become the most important non-invasive diagnostic tool in the daily practice of a pediatric cardiologist who predominantly deals with congenital structural heart disease in neonates and infants. Consequently, one-dimensional M-mode echocardiography has lost most of its importance particularly in this field. Therefore, an atlas showing exclusively two-dimensional echo cardiograms of the most common and some less frequently occurring malformations appeared to be a useful addition to the existing literature. The confinement to two dimensional imaging alone allowed an elaborate presentation of the various defects with more than 200 selected still frames and many additional explanatory drawings and diagrams. The material was collected from patients who were referred to the Department of Pediatric Cardiology of the Wilhelmina University Children's Hospital in Utrecht during a period of about 2 years. The two-dimensional echocardiographic findings were correlated with cardiac catheterization data and/or surgical procedures and/or post mortem investigations. The necessary echocardiographic equipment was aquired with financial aid from the Dutch Heart Foundation. We are indebted to Mrs. 1. W. Wetselaar for her outstanding artwork. We also thank P. D. Woltema and F. l. van Waert for the photographic reproductions, lacomine Bosma for preparing and type-setting the entire manuscript and Dr. N. Middleton for critically reading the English text. G. l. van Mill, M. D. A. l. Moulaert, M. D. E. Harinck, M. D. CONTENTS 1. Introduction and the normal heart 1 Introduction 1 T~~m~h~rt 2 2.