Ankylosing spondylitis (AS) is a chronic inflammatory disease of unknown cause, characterized by sacroiliitis and spondylitis. To date, treatment of AS has been limited to the alleviation of symptoms, mainly using non-steroidal anti-inflammatory drugs (NSAIDs). For patients refractory or intolerant to NSAIDs, the disease modifying antirheumatic drugs (DMARDs) have been used as a second line approach. Methotrexate (MTX) is currently one of the most widely used DMARDs and its efficacy in rheumatoid arthritis (RA) has been confirmed (Suarez-Almazor 2003). There is uncertainty whether MTX works in the treatment of AS.