The idea behind guided pathways is straightforward. College students are more likely to complete a degree in a timely fashion if they choose a program and develop an academic plan early on, have a clear road map of the courses they need to take to complete a credential, and receive guidance and support to help them stay on plan. However, most community colleges, rather than offering structured pathways to a degree, operate on a self-service or "cafeteria" model, allowing students to choose from an abundance of disconnected courses, programs, and support services. Students often have difficulty navigating these choices and end up making poor decisions about what program to enter, what courses to take, and when to seek help. Many drop out of college altogether. Many community college reform efforts have sought to improve rates of student completion by scaling up discrete interventions focused on only one element of the college experience. The guided pathways model, in contrast, entails a systemic redesign of the student experience from initial connection to college through to completion, with changes to program structure, new student intake, instruction, and support services. This research overview--part one in Community College Research Center's (CCRC's) guided pathways practitioner packet--describes the reform model and summarizes evidence supporting its design principles. [For "Implementing Guided Pathways at Miami Dade College: A Case Study" (part two), see ED562050. For "Implementing Guided Pathways: Tips and Tools" (part three), see ED562051.]