Investigators will conduct a 6-month assessor-blinded randomized-controlled trial of 200 community-dwelling adults with mild cognitive impairment. Individuals will be randomized to one of four experimental groups, all which receive 6 months of exercise classes four times per week: 1) combined aerobic training and resistance training; 2) aerobic training; 3) resistance training; or 4) balance and toning exercise. There will be two measurement sessions: baseline and 6 months (end of intervention period).