The clinical research landscape is gradually changing as we enter the era of big data. Big data sources are multiplying as existing sources collide to create expanded platforms that serve wider areas of expertise. Clinical study designs incorporating big data have started to appear and we expect this design phenomenon to grow. Big data offers unprecedented advantages in clinical research, but much remains to be done in assuring accessibility, validity, quality, and privacy protection. For these reasons, medical writers must understand big data, the strengths and the potential limitations of the data used, and should consider big data impact on study design, protocol, and clinical study report authoring. This article provides an overview of big data sources and provides insights on how big data utility could change the clinical regulatory medical writing landscape.