Police said 125,000 demonstrators marched Sunday to the Place de la Bastille, site of the French Revolution, to put pressure on the National Assembly, expected to discuss granting equal marriage and adoption rights to same-sex couples Tuesday, Radio France Internationale reported.
Already in the hopper are more than 5,000 submissions for amendments, officials said.
Paris' mayor, Bertrand Delanoe, who announced years ago that he was gay, was among those who marched Sunday. He said the changes being considered "wouldn't take anything away from anyone. It would make French society more free, more comfortable."
A survey published during the weekend by the French news website Atlantico indicated 63 percent of those surveyed supported gay marriage. Fifty-one percent said they were against granting adoption rights to same-sex couples.
RFI did not include a margin of error or other information about the poll.