Oprah had a surprise for every single member of the audience

A total of 276 Pontiac G6 sports sedans were given away to the all-female audience - worth $7m in all.

General Motors, which provided the cars, said the publicity coup made financial sense.

The Oprah Winfrey Show reaches 30 million Americans every week and is viewed in dozens of foreign countries.

At the opening of the show's 19th season on Monday, Oprah called 11 members of the audience to the stage, surprising them with new cars.

Anyone can run commercials, but you rarely get a chance to partner with someone of Oprah's stature Pontiac

She then handed out gift boxes to the rest of the audience, saying one contained a 12th free car.

At the count of three, all boxes were opened at the same time, unleashing shrieks of delight from every remaining participant.

The TV host had handpicked the members of her audience, all of them women. Their relatives had written in to the show to explain why they were a deserving case.

General Motors said the total value of the cars was equivalent to 50 prime time TV adverts.

"Anyone can run commercials, but you rarely get a chance to partner with someone of Oprah's stature," Mark-Hans Richer, Pontiac's marketing director, told AFP news agency.