Two ME patients will today launch a High Court appeal to argue that more emphasis should be put on medical rather than psychological treatment for their condition.
The pair, Kevin Short from Norfolk and Douglas Fraser from London, have brought the judicial review against what they say is an "unfair and irrational" approach by the NHS to those suffering with myalgic encephalomyelitis (ME).
In 2007 the National Institute for Health and Clinical Excellence (NICE) recommended cognitive behavioural therapy (CBT) and graded exercise therapy (GET) as frontline treatments.
But the two men will tell the High Court that more emphasis should be placed on drug treatments. Standard drugs are used to combat symptoms such as joint pain but the campaigners will argue that anti-viral treatments should be used more readily.
The ME Association is backing the case, describing the current guidance as "unfit for purpose".
However, NICE chief executive Andrew Dillon has said the guidance is "robust" and designed to improve care.
The hearing is expected to last two days.