Positive psychology is a rapidly emerging initiative within the social sciences, as evidenced by this book and other recent volumes devoted to positive psychology (e.g., Chang, 2001b;Gillham, 2000;Snyder & Lopez, 2002). To paraphrase Seligman (1998), positive psychology entails a focus on human strength as well as weakness, an interest in resilience as well as vulnerability, and a concern with cultivating wellness as well as remediating pathology. Positive psychologists seem to agree that optimism is an important construct to be included in this new approach to psychology (Peterson, 2000;Peterson & Steen, 2002).As optimism researchers, we are pleased to see optimism featured in what seems to be a long-needed antidote to psychology's focus on what goes wrong with people. But we are also aware of some questions that need to be considered for optimism to thrive as part of this new psychology of flourishing. Perhaps the most general question to be raised concerns the type of optimism most pertinent to flourishing. Optimism and pessimism are both complex concepts, and research to date usually renders them in simplistic fashion.In this contribution, we discuss optimism as studied within contemporary psychology, and we do so in the context of issues that might profitably be raised about the meaning of these concepts. Although empirical research into optimism has yielded a number of interesting and reliable findings, we believe that the best is yet to come, so long as optimism and pessimism are approached with sufficient conceptual and methodological sophistication. We begin by discussing the meanings of optimism and pessimism, focusing on distinctions that might be made within these constructs but rarely are. We illustrate the power of these distinctions in two ways: (a) by discussing how researchers might look more closely at data in light of them and (b) by summarizing research on the cultural context of optimism that makes most sense in terms of these distinctions.