This study is a double-blind, randomized, placebo-controlled trial of the safety and efficacy of creatine in patients with ALS enrolled at sites distributed throughout the United States, including Northeast ALS (NEALS) sites. The study will provide preliminary data on the safety and efficacy of creatine in ALS. If creatine slows disease progression in ALS and is well tolerated, a phase 3 study with survival as the primary outcome measure will be initiated.