Minocycline to Treat Amyotrophic Lateral Sclerosis

To be eligible for enrollment in this study, subjects must meet the following eligibility criteria within fourteen days prior to randomization: Inclusion criteria: * A clinical diagnosis of laboratory-supported probable, probable or definite ALS, according to modified EL Escorial criteria. * FVC greater or equal to 75% of predicted. * Onset of weakness within 3 years prior to enrollment. * If patients are receiving riluzole they must be on a stable dose for at least the past thirty days. * Women of childbearing age must be non-lactating and surgically sterile or using an effective method of birth control and have a negative pregnancy test (adequate birth control includes use of intra-uterine device or oral contraceptives plus a barrier method, e.g. condom, diaphragm). * Willing and able to give signed informed consent that has been approved by your Institutional Review Board (IRB). Exclusion criteria: * Requirement for tracheotomy ventilation (or non-invasive ventilation \> 23 hours/day). * Diagnosis of other neurodegenerative diseases (Parkinson's disease, Alzheimer's disease, etc). * FVC \< 75% of predicted. * A clinically significant history of unstable medical illness (unstable angina, advanced cancer, etc) over the last 30 days. * History of renal disease (screening creatinine greater than 1.5). * History of liver disease (screening alanine aminotransferase greater than 3 times the upper limit of normal). * History of hematologic disease (screening white blood cell count less than 3,800/mm3). * History of system lupus erythematosis (or screening ANA of 1:160 or greater). * Treatment with any medications that may cause lupus-like symptoms within 4 weeks of baseline visit (e.g. procainamide, hydralazine). * History of vestibular disease (excluding benign position vertigo). * Pregnancy or lactation. * Allergy to tetracycline antibiotics. * Use of minocycline within thirty days of enrollment (baseline visit). * Use of anti-epileptic medications other than gabapentin. * Limited mental capacity rendering the subject unable to provide written informed consent or comply with evaluation procedures. * History of recent alcohol or drug abuse or noncompliance with treatment or other experimental protocols. * Use of any investigational drug within the past 30 days (Creatine, Vioxx, Celebrex, Topiramate). * Women with the potential to become pregnant who are not practicing effective birth control.