More than 100,000 people rallied across France against government plans to approve same-sex marriage and adoption, as police clashed with counter-demonstrators in one city.
Wearing pink scarves and T-shirts and carrying pink and blue balloons with the image of a man and woman holding two children, demonstrators marched against reforms planned by the socialist government.
They marched under banners that carried slogans such as "Pro-marriage, not anti-gay" and "Long live the true family". A Roman Catholic humorist who goes by the name of "Frigide Barjot" opened the Paris protest.
"We are born from a man and a woman," she told the crowd. "A child is the result of a man and a woman's orgasm."
Some 70,000 people joined the Paris rally on Saturday, police said - though organisers put the figure at 200,000 - with more than 30,000 others holding similar protests around the country.
In the southeastern city of Lyon, 22,000 people protested, police said. Officers there detained around 40 youths who had come to oppose the main rally.
And police in the southwestern city of Toulouse used tear gas against a group of several hundred activists who tried to confront the main rally of several thousand in a counter-protest.
Up to 8,000 marched in the southern city of Marseille, where they too were confronted by supporters of gay marriage. There were other protests in Rennes and Nantes in the northwest, and in Laon in the north.
Women's rights minister and government spokeswoman Najat Vallaud-Belkacem defended the right of homosexuals to marry and to adopt as representing progress for everyone.
Parliament would in any case consult widely on the issue and this would be the time for debate, she added, warning against excess and polemic.
French President Francois Hollande's government has come under fire from Catholic groups and the right-wing opposition over the bill.
The marches came as Pope Benedict called on the French church on Saturday to make its voice heard on social issues.
Organisations backing the rallies included a group of homosexuals opposed to the bill called More Gay Without Marriage; the Left for Republican Marriage; and a French Muslim group called Sons of France.
Anti-abortion group Alliance Vita also backed the campaign.
Protester Beatrice Bodji said she had come because "children are taken hostage" if same-sex marriage and adoption are allowed.
"It's scandalous that the government wants to institutionalise a state lie by hiding the fact that the basis of every child is a dad and a mom," Jean-Marie Barbiche, who came with his wife and four children, said.
Fanny Neige and Anais, two homosexual counter-demonstrators, staged a rally of their own, kissing each other in front of the crowd.
"We'll start a family whether they want us to or not," said Fanny Neige.