This cross-sectional study examined associations among aerobic capacity, muscle strength, balance, and cognitive processing speed (CPS) in 31 persons with multiple sclerosis (MS) and 31 matched controls. Participants completed neuropsychological tests and aerobic capacity (i.e., peak oxygen consumption), muscular strength (i.e., asymmetry between knee muscles), and balance (i.e., postural sway) assessments. Aerobic capacity (r =.27), postural sway (r =.40), and knee extensor asymmetry (r =.25) were associated with CPS in those with MS and accounted for differences in CPS between MS and control groups. Such cross-sectional data suggest that aerobic, balance, and resistance training might be avenues for improving CPS in this population. The authors report no conflicts of interest and thank Swathi Balantrapu, Jason Silberman, Stefanie Fitterer, and Rachel Japp for assistance in data acquisition. © 2012 Copyright Taylor and Francis Group, LLC.