This issue of Seminars of Medical Genetics features a series of articles on human disorders caused by the dysregulation of imprinted genes. At the outset, there is a review of the general mechanisms by which genomic imprinting is normally regulated followed by an exploration of the clinical and molecular aspects of human imprinting disorders. As we enter an era of bioinformatics and genome-wide analyses with increasing access to high density microarrays and next generation sequencing, it is becoming apparent that the concept of a single mutation or epimutation leading to a disease is outdated. The role of the clinician will become increasingly important, in concert with these molecular advances, in terms of evaluating phenotypic variation to further our understanding of imprinting disorders. Such investigations will benefit children and families as we become better able to define recurrence risk, predict phenotype, and tailor medical management. © 2010 Wiley-Liss, Inc.