 To our knowledge, the only randomized clinical trial using MP in persons with MS assessed the effect of this medication on attention, reporting significant improvements in cognitive task performance PASAT in the MP treatment group Harel, Appleboim, Lavie, Achiron, 2009 as compared to a placebo control group. While an expert opinion paper sponsored by the NMSS recommends the use of MP to treat fatigue Expert Opinion Paper, 2006, to our knowledge, no clinical trials have been conduced to objectively test the effect of MP administration on fatigue in individuals with MS and support this recommendation. The current study will fill this void in the literature. Aim 1: We propose to test the efficacy of MP on decreasing self-reported fatigue in individuals with MS in a double blind placebo controlled randomized clinical trial DBRCT. Aim 2: We will also examine the effects of MP on cognitive functioning. Based on the existing literature on MP Bales, Wagner, Kline, Dixon, 2009; Harel et al., 2009, we expect that MP will enhance processing speed and attention, with little impact on other cognitive functions such as memory or executive control. 