Digenic inheritance (DI) of a disease in a family means that the variants at two genes or loci explain which individuals are affected or unaffected more clearly than the genotypes at one locus alone.  This article catalogs case studies of human DI, since the first such example was published in 1994. One objective is to evaluate which strategies to find DI worked best in the past. Another objective is to consider new possibilities of using high-throughput sequencing (HTS) and improved knowledge on protein-protein interactions (PPIs) to facilitate the discovery of new instances of DI. Researchers evaluating new possible instances of DI can use the catalog to compare the strength of their evidence to that of past DI case studies. (By Dr. Alejandro Schaffer, http://jmg.bmj.com/content/early/2013/06/18/jmedgenet-2013-101713 )