||The primary objective of the study is to determine the acute safety and tolerability of oral administration of Gilenya (fingolimod) 0.5mg daily vs. matched oral placebo administered daily. The primary outcome measure will be safety and tolerability; safety will be assessed by the occurrence of adverse events and clinically meaningful changes in vital signs, ophthalmologic examination, physical examination, electrocardiogram and standard clinical laboratory blood tests, and tolerability will be defined as the ability of subjects to complete the entire 4-week study. The secondary outcome measure will be the measured effect of the treatment on circulating lymphocyte populations in patients with ALS. Exploratory outcome measures will include the rate of decline of the ALS Functional Rating Scale (Revised) (ALSFRS-R) and Slow Vital Capacity (VC) during the course of treatment. This study will be conducted in subjects who meet the El Escorial criteria of possible, laboratory-supported probable, probable, or definite criteria for a diagnosis of ALS. At screening, eligible subjects must be at least 18 years old, must have an SVC ≥ 65% of predicted capacity for age, height and gender, and must provide written informed consent prior to screening. Subjects on a stable dose of riluzole and those not taking riluzole, and women of child-bearing age at screening are eligible for inclusion as long as they meet specific protocol requirements. Subjects will remain on randomized, placebo-controlled, double-blind treatment until the Week 4 visit. Each randomized subject will also have a Week 8 Follow-up Telephone Interview to assess for adverse events (AEs), changes in concomitant medications and to administer the ALSFRS-R.