Twenty four British music festivals have banned the sale of legal highs, which have been blamed for 68 deaths in 2012.
The Association of Independent Festivals said its members will also take part in a digital blackout to highlight the issue.
The websites and social media accounts of the festivals will go dark for a day on Monday.
The association said it needs to make fans aware of the dangers of legal highs and help them make safer choices when having fun.
Music fans visiting the homepages of the festivals will see a completely black window except for a grey light bulb and the message "Don't be in the Dark about Legal Highs".
