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Emerging evidence indicates that age-related decline in higher order cognitive processing, e.g. attention and executive functioning, is associated with impaired gait and is important in relation to falls in older adults (Yogev-Seligmann et al., 2008; de Bruin and Schmidt, 2010; Mirelman et al., 2012). There are strong indications that the most important risk factors for cognitive decline, dementia, impaired gait, and falls in older adults are interconnected and are modifiable through physical activity and training as well as partly through cognitive training (Stenhagen et al., 2013; Baumgart et al., 2015; Hortobagyi et al., 2015; Van Abbema et al., 2015; Liu et al., 2016). However, since to date, to the best of our knowledge, no interventions have studied synergistic or cumulative effects from multicomponent physical exercise programs with additional cognitive training to improve cognitive performance, brain function, gait, and prevent falls. Moreover, the neurophysiological mechanisms mediating the effects of physical training on cognition and brain function in older adults remain unclear. Therefore, the aim of this thesis is to illuminate the effects of interactive simultaneous cognitive–motor training modalities on cognitive and brain function, cognitive–motor dual-task walking, and fall prevention in older adults. Study 1 (chapter 3) addresses the question of how good the cognitive and physical fitness status of Swiss older adults, as assessed with cognitive–motor dual-task gait speed measurements, is in relation to the requirements that are necessary to stay independent as a pedestrian in an urban environment. This cross-sectional study with 120 participants establishes the relevance of investigating effective training interventions for older adults, which are in the focus of the subsequent interventional studies 2a/b and 3. Thus, as a second step, a 6-month longitudinal training intervention study with a 1-year follow-up is performed, including 89 participants, to investigate both broad cognitive (study 2a, chapter 4) and physical adaptations, including dual-task gait measures and fall frequency (study 2b, chapter 5). Finally, in a third step, a shorter 8 weeks lasting training intervention study is conducted, including 42 participants, to address the question if the training-induced cognitive behavioral adaptations, that were observed in study 2a, would be reflected in brain functional adaptations in older adults (study 3, chapter 6). The main findings from study 1 include that about every third (35.6%) older person at the age of 70–79 years and almost three-quarters (73.8%) of persons ≥80 years cannot walk faster than 1.2 m/s, which is required to cross streets safely within the green–yellow phase of pedestrian lights, under cognitively challenging conditions. Study 2a demonstrates, first, that the two interactive simultaneous cognitive–motor programs are partially advantageous to boost performance in two measures of executive function (switching attention and working memory) compared to an exclusively physical training program; and second, that cognitive performance, including executive functions, long-term visual memory (episodic memory), and processing speed, is maintained until 1-year follow-up after all three interventions. Study 2b shows, first, that the two interactive simultaneous cognitive–motor programs result in a significant advantage in dual-task costs of walking compared to the exclusively physical program but not in any other gait variables; second, that the two simultaneous cognitive–motor interventions lead to different training-specific adaptations in the rhythm and variability domains of gait; and third, that each of the three training programs very effectively reduced fall frequency for ~77%. Finally, Study 3 reports, first, that both the video game dancing and the balance interventions reduce left and right hemispheric prefrontal cortex (PFC) oxygenation during the acceleration of walking, while video game dancing showed a larger reduction at the end of the walking phase compared to balance training in the left PFC; and second, that the exercise training-induced modulations in PFC oxygenation are associated with improved executive functions. The main conclusions from this thesis imply that the fitness status of many older adults is not appropriate to safely encounter the requirements for pedestrians in urban areas, which reinforces the need for regular cognitive and physical training in the older population (study 1). Interactive simultaneous cognitive–motor training should be integrated in training programs aiming to improve cognition, gait performance, physical functioning, and reduce fall frequency in older persons. Such programs may potentially counteract the large prevalence of cognitive and gait impairments, as well as reduce fall fre- quency, inherently leading to more independence and a better quality of life (studies 2a/b). Finally, training-induced brain functional adaptations in the PFC seem to reduce the need of prefrontal resources of executive function and attention involved in challenging treadmill walking. This effect may liberate cognitive resources to focus on other processes while walking in attention demanding real-life situations such as crossing streets or walking while talking and could potentially reduce the risk of falling (study 3).