or over two million years, humans have strived to live harmoniously with nature. Early ancestors found that being outdoors often requires high physical endurance and labor such as chasing after prey, traveling across mountain ranges, and cultivating farms (Bramble & Lieberman, 2004). Heinrich (2001) described the evolutionary pressure to travel farther and faster in his book, Why We Run: "For millions of years, our ultimate form of locomotion was running" (p. 9). However, modern advances in technology and urban living provide people with resources such as bicycles and motor vehicles, so they no longer have to depend on their physical skills for survival. Over the past 20 years, there has been a dramatic increase in a sedentary lifestyle and a decrease in overall physical activity (Ernersson, Lindström, Nyström, & Frisman, 2010). Instead of hunting or cultivating land for food, people drive to grocery stores and consume high-caloric meals at restaurants. Although modern living is beneficial and desirable for many, it may diminish the opportunity for an active and healthy lifestyle. Physical and Psychological Well-Being Exercise and an active lifestyle contribute to physical and emotional health and well-being (World Health Organization, 2005). Nevertheless, many people fail to incorporate exercise into their daily routines: National statistics have indicated that ABSTRACT. Ultramarathons, races extending beyond the traditional 26.2 mile marathon, have become increasingly popular over the past decade. Ultrarunners run longer distances and spend extended periods of time in nature compared to short-distance runners. The present study examined the role of distance and nature on runners' flow (i.e., complete absorption in the present moment) and well-being. One hundred eighty-nine runners (132 women, 57 men, M age = 35.93 years, SD = 9.66) completed an online survey assessing running distance, running environment, flow (Jackson & Marsh, 1996), personality (TIPI; Gosling, Rentfrow, & Swann, 2003), and well-being (Côté, Gyurak, & Levenson, 2010). Independent t tests revealed that ultrarunners spent more time in nature (p = .001), were more neurotic (p = .04), and experienced greater flow (p = .001) than short-distance runners, but did not differ in well-being. Multiple regression analyses indicated that being an ultrarunner, running in nature, conscientiousness, and openness significantly predicted flow, F(7, 163) = 8.48, p = .001, R 2 = .27. Running environment and personality (i.e., extraversion, conscientiousness, and openness) predicted greater well-being. However, contrary to expectations, running in a nonnatural environment was related to greater well-being, but being an ultrarunner and flow were not, F(8, 161) = 4.57, p = .001, R 2 = .19. Findings suggested that, although distance and nature contribute to flow, running in general may have a more profound impact on well-being than immersing oneself in nature.