Mardi Gras marchers donned wigs, harnesses and hotpants - as well as wedding gear - as they campaigned for gay equality in Sydney's annual parade.

The weather was wet and the clothing miniscule but that did not stop the party along Oxford Street.

Floats of brides and brides and grooms and grooms, dressed both traditionally and extravagantly, strutted their stuff in a statement about equality.

The theme of this year's event was 'say something', with 15 of the 130 floats addressing the issue of same-sex marriage.

Organisers set up speech bubbles along the parade route and called on spectators to speak out against inequity.

The parade was led by eight people who organisers say have made a difference in the lives of gay people.

They included openly gay actress Lily Tomlin, gay rights campaigner Peter Tatchell and two Melbourne teens who protested against the ban on gay couples at a school formal.

New South Wales Labor Minister Verity Firth said thousands of spectators were expected to line the parade route.

"Mardi Gras has been an unmistakable part of Sydney life," she said.

"We must never forget that the first Mardi Gras in 1978 was about the struggle for equality and this aspect remains absolutely a part of the parade today."

New Mardi Gras chief executive Michael Rolik says the event does not only benefit the gay community.

"In terms of economic impact it is the second-largest event in the state," he said.

"At last tally it generates an annual income in terms of economic benefit ... of about $30 million for the state of New South Wales."

Around 1,000 police officers and dozens of paramedics patrolled the parade route and and so far there have been no reports of arrests or major incidents.

The Mardi Gras is the longest running event of its kind in Australia.