French fashion's two biggest players, LVMH and Kering, said this month that they were banning ultra thin and underage models from their catwalks.
The two companies -- which between them control a raft of storied labels from Christian Dior and Louis Vuitton to Saint Laurent and Balenciaga -- have vowed to use only models 16 and older from now on.
The girls must also be at least size 34 (size six in Britain, 0 in the US).
Models must also have a medical certificate proving they are not overly thin and in good health, in keeping with a French law passed in May.
Although the pledge by the two conglomerates, which dominate the global luxury brands market, came in time for fashion weeks in London, New York and Milan -- which ends Monday --the sheer scale of Paris will show how much other labels follow suit.
"At the moment Paris is where the most shows are... and I was beginning to feel it was like the Wild West," James Scully, the American casting director, told AFP in New York.
Scully spoke out about the way models were treated during Paris fashion week last February, when many had to wait hours in a stairwell to try out for a Balenciaga show.
"The main reason I did it was the influx of models that were too young to be doing this and the fact that they were so disposable," Scully said.
"A lot of people really took notice."
Models 'won't be messed around'
He said he was cheered by designers who do not work for either Kering or LVMH who also seem to have got the message.
"I did have a few people reach out, designers that were trying to keep that going," Scully said.
But he said the "most important thing is having seen all the girls, they're not going to be messed around now."
And he defended the use of Kaia Gerber, daughter of former supermodel Cindy Crawford, who became a star of the New York catwalk despite having only just turned 16.
"A girl like Kaia is already with the best agency in the world and has a mother who has been through this. She'll be very protected," he said.
Saint Laurent's spring/summer show on Tuesday is likely to come in for particular scrutiny after an outcry in March over its use of very thin models in "porno chic" poses for an publicity campaign which drew the ire of France's advertising authority.
The ban on ultrathin models imposed by its parent company, LVMH, also extends to advertisements.