Objective.: The aim of this study was to test the assumption that the level of outdoor physical activity mediates the relationship between fear of falling and actual outdoor falls according to the Task Difficulty Homeostasis Theory. Method.: A prospective follow-up study of 10 months conducted in the year 2000 in three municipalities in the province of Friesland, The Netherlands. The participants were 1752 people aged 65 and older, living independently, in the community. Main baseline data were age, sex, outdoor physical activities (walking, bicycling), and fear of outdoor falls. The number of people who fell outdoors was recorded. Results.: People with a high fear of falling were more often low to moderately active or active compared with people who had no such fears and were more often very active. Fear of falling was not associated with outdoor falls, but it was after taking the level of physical activity into account. Conclusions.: Outdoor physical activity mediates the relationship between fear of falling and actual outdoor falls. This implies that the incidence of falls as an outcome in studies does not adequately represent the impact of risk factors for falls and that level of physical activity should be taken into account.