A judge has ruled that the National Institute for Health and Clinical Excellence (NICE) must change its "discriminatory" guidance in relation to three Alzheimer's drugs.
Mrs Justice Dobbs, sitting at the High Court in London, said the tests used to assess Alzheimer's are discriminatory against people with learning difficulties or those with English as a second language.
But campaigners have been left bitterly disappointed as the judgement does not open the door for thousands of people in the early stages of dementia to get access to the drugs.
NICE decided last year that Aricept, Reminyl and Exelon should not be provided on the NHS to people with early-stage Alzheimer's.
However, in the first court challenge of its kind against NICE, Eisai, the Japanese firm which makes Aricept, and distributor Pfizer, accused the organisation of acting "irrationally and unlawfully".
NICE said its guidance that the drugs should only be prescribed to those in the moderate stages of the disease had been challenged on six grounds - and the judge "found in our favour on five of them".
Chief executive Andrew Dillon said: "This ruling strengthens NICE by endorsing our approach to evaluating drugs.
"Our guidance stands and the drugs continue to be recommended only for people with moderate Alzheimer's disease, but the court has asked us to clarify our guidance when it is used for certain groups."