This thesis focuses on the signaling and trafficking functions of β-arrestins, which are critical regulators and transducers for the large G protein-coupled receptor (GPCR) family. The introductory chapter will briefly cover GPCR biology, how the β-arrestins were discovered, the current understanding of the GPCR/β-arrestin complex and how it affects the core β-arrestin functions of desensitization, internalization, and β-arrestin-mediated signaling. The second chapter describes a new cellular mechanism for β-arrestin function termed ‘catalytic activation’ where β-arrestins briefly bind to GPCRs, become activated, and then remain active after dissociation. The third chapter explores the role of phosphoinositides in β-arrestin conformation and function. The fourth chapter will discuss new approaches to understanding the conformational states of β-arrestins. The fifth chapter describes a new mechanism of βarrestin-mediated trafficking and provides a framework for understanding how β-arrestins transduce receptor-specific functions. The final chapter summarizes some major advances, discusses how these fit with the established findings, and suggests future directions.