Congenital defects of lymphatics constitute a spectrum of disorders that may manifest with a variety of clinical presentations including lymphedema, chylous effusions, lymphangiomatous malformations with cystic masses and localized gigantism, and intestinal lymphangiectasia with malabsorption. These entities constitute a relatively rare group of disorders, the origin of which remains somewhat controversial, but in some it appears to be due to early lymphatic obstruction. Five cases are described, which demonstrate the anatomical pathology of these entities. A classification and description of the defects is also presented. An attempt is made to present a unified theory of origin for this seemingly diverse group of diseases. While these entities may be challenging from a diagnostic and therapeutic standpoint, a wide variety of imaging modalities, which includes lymphography, computed tomography scanning, and ultrasound, may be used to diagnose the extent and internal structural characteristics of the abnormalities.