The lambda was selected as a symbol by the Gay Activists Alliance of New York in 1970, following the Stonewall Riots, and was declared the international symbol for gay and lesbian rights by the International Gay Rights Congress in Edinburgh, Scotland, in 1974. The lambda signifies unity under oppression.
The Scottish Minorities Group hosted the first ever International Gay Rights Conference in Edinburgh from 18 to 22 December 1974. It was co-organised by Ian Dunn and Derek Ogg. Ian Dunn had organised the first meeting of what was to become the Scottish Minorities Group in 1969. Derek Ogg later founded Scottish AIDS Monitor in the 1980s.
The conference tried to provide an international sharing of experience, so that delegates could find out the social, political and legal situation for men and women from other countriesm, and included sessions on the rights of young homosexuals and of gay women. The problem of lesbian invisibility was explicitly addressed by a delegate from Campaign Against Moral Persecution in New South Wales, Australia.
Nearly 400 people attended the conference, which led in 1978 to the establishment of the International Gay Association, later to become the International Lesbian and Gay Association (ILGA).
The gay rights organization Lambda Legal and the American Lambda Literary Award derive their names from this symbol. Gay News offered a range of jewellery items featuring the Lambda symbol.