The Lifelong Learning Imperative (LLI) project was initiated to assess current practices in lifelong learning for engineering professionals, reexamine the underlying assumptions behind those practices, and outline strategies for addressing unmet needs. The LLI project brought together leaders of U.S. industry, academia, government, and professional societies to assess the current state of lifelong learning of engineers; to examine the need for, and nature of, lifelong learning going forward; and to explore the responsibilities and potential actions for the primary stakeholders. The United States is facing a crisis in its engineering workforce just as global competition is becoming very intense. During the next several years there will be massive retirements of skilled and experiences engineers, and the United States has one of the lowest rates of graduation of bachelor-level engineers in the world: only 4.5 percent of our university graduates are engineers. The issue is especially acute in the national security industry because of citizenship requirements. Perhaps even more critical, the pace of technological change continues to accelerate, making the specifics of engineering education and skill development obsolete in short order. A critical part of our corporate and national strategy to address this looming crisis should be to ramp up the quality of engineers' professional life, improve their capacity to innovate, and widen their fields of opportunity. A project-framing workshop was organized by the University of Illinois at Urbana-Champaign (UIUC) in partnership with the National Academy of Engineering in June 2009 to examine the issues relevant to lifelong learning in engineering. A UIUC research team then conducted a survey-based assessment of the issues identified in the 2009 workshop. Preliminary findings from the UIUC study were examined more fully. "Lifelong Learning Imperative in Engineering" reflects the opinions of the authors based on the UIUS team's survey analysis and learning from the discussions at the 2011 workshop.