This paper describes the next steps for establishing detailed, useful behavioral phenotypes and for moving forward in the study of the relationships among genes, the environment, and language disorders. Key issues are recognizing the continuum of language behaviors to accurately describe disorders and the spectrum of typical development. A coordinated plan with foundational studies that address definition, measurement, design, and analytical methods is needed. Researcher capacity must be increased, and a greater focus on communication across disciplines to successfully accomplish interdisciplinary research is required. Language is not static, even in disorders; thus, we must study change over time. It is necessary to think about behavioral phenotypes in terms of developmental trajectories. Finally, data sharing and ethical and legal issues must be addressed.