In the nearly 50 years since the description of Williams syndrome by [Williams et al. (1961); Circulation 24:1311-1318], the focus of scientific inquiry has shifted from identification, definition, and description of the syndrome in small series to genotype-phenotype correlation, pathophysiologic investigation in both humans and in animal models, and therapeutic outcomes in large cohorts. Study of this rare syndrome has provided insight into the structure and function of the extracellular matrix, has contributed to understanding of genomic structure and rearrangement, and is beginning to elucidate genetic underpinnings of learning, language, and behavior. The results of current research not only recommend interventions that can be implemented now, but also identify areas requiring additional investigation, and suggest future therapeutic approaches.