Its first parade in 1997 was attended by 2,000 people.
By 2003, participation hit one million and from 2006, the annual parade in Brazil's largest city with a population of 11 million hit the three million mark and at 3.5 million in 2007.
Although organisers said on its website that four million people are expected this year, news reports put the figure at around three million.
The theme this year is "Vote against homophobia" as a reminder for LGBT Brazilians and their allies to "pay attention to the political debate on gay issues in an year where Brazilians are voting to elect the next President as well as the Senate and Congressmen," read the parade's official website.
Brazil's news portal Uai.com reported that a 198 people were killed last year in homophobic and transphobic attacks.
The Associated Press reports: "Millions of gays and lesbians have jammed several of Sao Paulo's main avenues for the 14th annual gay pride parade in South America's largest city.
"A river of gay men, lesbians, cross dressers and even heterosexual couples flowed down skyscraper-lined Avenida Paulista in what is billed as the world's biggest gay pride parade."
The 4.2 km parade started at Avenida Paulista (MASP) at around noon on Sunday, June 6, and ended at Praça Rooselvelt, in Downtown Sao Paulo, at around 10pm.
Sister city Rio de Janeiro will have its pride parade on Oct 10, 2010.