This reflective personal account traces phases of the author's career where he saw psychology as relevant to major world problems. Chronologically, these problems included issues of international conflict, waste of energy and natural resources, human behaviors that caused environmental destruction, and the paramount threat of global climate change. Psychologists can make valuable contributions to describing, evaluating, and resolving these problems, and their vital importance should motivate the research and teaching of many psychologists. Our generation's success in achieving sustainable patterns of living on the Earth will determine whether the Earth will retain a livable environment for future generations. Brief suggestions are offered for approaches that may lead to more effective research and advocacy on crucial social issues.