In this commentary, I highlight key insights from research on learning disabilities (LD) reported in this special issue. Authors of each article describe innovative work that is expanding frontiers of LD knowledge, by focusing on vulnerable and understudied populations, using multiple methodologies and data sources, and building and refining theory. Insights that emerge from this work relate to defining and identifying LD; estimating prevalence rates of LD subgroups; and understanding the role of cognitive, language, genetic, and environmental factors and their implications for assessment and intervention. I conclude that findings of this work promise to have a significant and lasting impact on the lives of children and youth with LD.