Evidence is accruing for the importance of cognitive mechanisms in chronic insomnia. This article summarizes and discusses recent evidence on five cognitive processes: worry and rumination, monitoring for threat, misperception of sleep, unhelpful beliefs about sleep, and safety behaviors that prevent disconfirmation of unhelpful beliefs. Emerging prospects garnering clinical and experimental interest in insomnia, including savoring and positive thinking, expectations about sleep, and daytime cognitive processes, are discussed. The article concludes with a discussion of treatment implications.