The purpose of this study is to evaluate the safety and effectiveness of creatine treatment in amyotrophic lateral sclerosis (ALS). There is currently no known effective treatment for ALS. It is known that nerve cells die in the brains and spinal cords of patients with ALS but the cause of the cell death is unknown. It has been shown that there is overactive nerve activity due to increased levels of a chemical called glutamate and that there is abnormal cellular metabolism along with increased production of substance called "free radicals." Improving cellular metabolism and readjusting the activity of glutamate in the brain may be beneficial to ALS patients.