Large-scale sequencing tests, including whole-exome and whole-genome sequencing, are rapidly moving into clinical use. Sequencing is already being used clinically to identify therapeutic opportunities for cancer patients who have run out of conventional treatment options, to help diagnose children with puzzling neurodevelopmental conditions, and to clarify appropriate drug choices and dosing in individuals. To evaluate and support clinical applications of these technologies, the National Human Genome Research Institute and National Cancer Institute have funded studies on clinical and research sequencing under the Clinical Sequencing Exploratory Research program as well as studies on return of results. Most of these studies use sequencing in real-world clinical settings and collect data on both the application of sequencing and the impact of receiving genomic findings on study participants. They are occurring in the context of controversy over how to obtain consent for exome and genome sequencing.