Inclusion Criteria:

• Diagnosis of ALS confirmed by the following definition:

  (a)"Probable" or "Definite" Amyotrophic Lateral Sclerosis (ALS) according to the El Escorial criteria(b)"Peripheral" onset form (limb involvement) or a "Bulbar" form of ALS with a duration of five years, based on inquiry for the earliest symptoms of the disease

• A subject who simultaneously presents with bulbar and peripheral signs at onset of ALS disease should be stratified to the bulbar onset group. The neurologic progression of such subjects matches that of the bulbar onset ALS subjects.
• Pulmonary Function: forced vital capacity (FVC) must be 3 60% at study entry.
• Females of childbearing potential must be documented to be using acceptable birth control methods such as an IUD or oral contraceptives.

Exclusion Criteria:

• Previous treatment with riluzole
• Tracheostomy, or expected to undergo a tracheostomy within two months after study inclusion
• Signs of clinical dementia and/or major psychiatric disorders
• Serious concomitant disease or handicap likely to interfere with the subject's assessments or impact on the subject's survival
• A multiple conduction block has been shown on nerve conduction studies by electromyogram

The above information is not intended to contain all considerations relevant to a patient's potential participation in a clinical trial.