Estelle, Annie Lennox and actor Jamie Bell have called on their online fans to help raise awareness of HIV and AIDS.
American Boy hitmaker Estelle is a longtime supporter of the Virgin Unite initiative, which aims to help young people stop the spread of the diseases.
To mark World AIDS Day on Thursday (01Dec11), she's penned a special message on her website calling for her followers to highlight the issue.
She writes, "My darlings... Join me, and millions of RED and ONE supporters, to Ã¯¬ght for an AIDS Free Generation by 2015. Add your voice. Make a pledge. Get a song from The Killers for free as a thankyou. The beginning of the endofAIDS starts with you."
Annie Lennox, who is due to speak at Britain's Houses of Parliament for a conference on international development on Thursday, has also used her website to recognise the important day.
The former Eurythmics star tells fans, "Click on the actions listed below to find out about some of the different ways you can get involved and show your support... Donate to The SING Campaign... Post a message of support on Twitter tagging WorldAidsDay and theSINGcampaign... Post a message of support on Facebook."
In a post on her Twitter.com page, Alicia Keys writes, "I have a feeling this is going to be a momentous day!!", while gay British actor/comedian Stephen Fry adds, "Around 20 people are diagnosed with HIV every day in the UK: please support THTorguk today for World Aids Day: the work they do is stunning."
Bell tells fans, "World Aids Day today! Retweet and raise awareness!"