398 Journal of Aging and Physical Activity, 2009, 17, 398-415 © 2009 Human Kinetics, Inc. Feasibility and Effectiveness of a Walking Program for Community-Dwelling Older Adults With Mild Cognitive Impairment Jannique G.Z. van Uffelen, Marijke J.M. Chinapaw, Marijke Hopman-Rock, and Willem van Mechelen This study examined the feasibility and effect on aerobic fitness of a 1-yr, twice- weekly, group-based moderate-intensity walking program (MI-WP, n = 77) compared with a low-intensity activity program (LI-AP, n = 75) for community-dwelling older adults with mild cognitive impairment (MCI). Thirty participants did not start a pro- gram; median attendance in the other 122 participants was 71%. Small but significant associations were observed between attendance and memory in the MI-WP and gen- eral cognition in the LI-AP. Associations were no longer significant when both groups were analyzed together. Intensity, assessed using percentage of heart-rate reserve and the Borg scale, equaled intended intensity for both programs. Aerobic fitness improved significantly in participants in the MI-WP. In conclusion, cognition was not clearly associated with attendance in the 62 participants starting the MI-WP, and average attendance was good. The intensity was feasible for participants who continued the MI-WP. The findings support the proposal that regular moderate-intensity walking improves aerobic fitness in adults with MCI. Keywords: cognition, exercise, aerobic fitness, randomized controlled trial Older adults are encouraged to pursue active lifestyles (Nelson et al., 2007). In the long term, physical activity, and more specifically aerobic exercise, can prevent the development and progression of age-related chronic diseases such as cardiovascular disease and diabetes (Nelson et al.; Peel, McClure, & Bartlett, 2005; Taylor et al., 2004). Other benefits of regular aerobic exercise include improvements in overall functioning because of enhanced physiologic capacity (Bean, Vora, & Frontera, 2004), better mental health (Netz, Wu, Becker, & Tenen- baum, 2005), and improved cognitive function (Colcombe & Kramer, 2003). Most studies on the benefits of physical activity and exercise for older adults have focused on those who are cognitively healthy (Bean et al., 2004; Taylor et al., van Uffelen is with Body@Work, Research Center Physical Activity, Work and Health, TNO-VU University Medical Center, the Netherlands. Chinapaw and van Mechelen are with the Dept. of Public and Occupational Health, EMGO Institute for Health and Care Research, VU University Medical Center, Amsterdam, the Netherlands. Hopman-Rock is with the Dept. of Physical Activity and Health, TNO Quality of Life, Leiden, the Netherlands.