The message is underlined by a poster featuring a close-up of a woman's breasts with condoms over her nipples and the line: "Nothing should take your mind off safe sex."
Admedia is buying media for the campaign, which is adopting a strategy of making the work unmissable for its target audience.
The posters will be on display above urinals and hand dryers. They will also work as point-of-sale material near condom machines to remind young men during the course of their evening to protect themselves and their partners.
More than 50,000 people are affected by HIV in Britain and the number of heterosexuals being diagnosed with the disease is increasing.
The Positive Place was founded ten years ago by a group of HIV-positive people who identified the need for a localised service for those living with HIV and Aids.
The charity now operates a network across South London. More than 5,000 people a year use its services, which range from self-help groups to encouraging people to develop and learn new skills.
The ad was written by Clive Pickering and art directed by Neil Dawson.
Pickering said: "There's a growing complacency among heterosexuals to HIV which needs to be addressed. The sites that Admedia has identified would make it very difficult for them to be overlooked."
The campaign comes amid fears that the number of Britons infected with HIV will rise by almost 50 per cent by 2005. Although homosexual and bisexual men remain most at risk, the number of new cases in heterosexuals exceeded new cases among gay men in 2001 for the third year in a row.