Multiple sclerosis has been grouped into several main types. These include:

• Relapsing-remitting MS — characterized by clearly defined attacks (relapses) followed by complete or partial recovery (remissions); most common form (75% at the time of diagnosis).
  
  
• Primary-progressive MS — less common (10 to 15% at time of diagnosis), people with this type of MS have a nearly continuous worsening of MS from the beginning with no clear relapses or remissions.
  
  
  
• Secondary-progressive — about half of people with relapsing-remitting MS start to worsen within 10 years of diagnosis, with possibility of increasing levels of disability.
  
  
  
  
• Progressive-relapsing — relatively rare, combines attacks with steady worsening from the onset of the disease.
  
  
  
• Benign MS — few attacks with long periods of remission and little disability after 15 years; about 20 - 25% of people who were diagnosed originally with relapsing-remitting MS have this type.
  
• Malignant MS — rapidly progressive disability within five years of diagnosis; rare.