A topless protester launched herself at Bill Cosby as he arrived for a retrial on sexual assault charges.
The woman had "Women's Lives Matter" written in red ink on her chest and stomach, and other phrases in red and black all over her body.
She was intercepted by police as she jumped over a barricade outside the courthouse in Philadelphia.
Cosby, 80, appeared startled but was untouched and uninjured.
He was led into the courthouse as the woman was led away in handcuffs.
She was among about half a dozen people showing support for Cosby's accuser, Andrea Constand.
Ms Constand alleges that the comedian drugged and sexually assaulted her at his home in 2004 when she was director of women's basketball at Temple University.
A judge has ruled that as many as five other women can testify alongside her.
The TV star, who is facing three counts of aggravated indecent assault, denies the accusations against him and claims the relationship with Mrs Constand was consensual.
Each count is punishable by up to 10 years in prison.
An earlier trial, in which Cosby faced the same accuser, ended in a hung jury last June.
Cosby is represented this time by a new lawyer, Tom Mesereau, who helped get Michael Jackson acquitted when he was accused of child molesting.
The defence team will be able to call on a witness who claims Ms Constand talked about framing a celebrity and was motivated by money.
Mr Mesereau is expected to focus on the amount Ms Constand was paid when she reached a settlement in a civil lawsuit in 2005.
The figure has never been disclosed.
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Ms Constand is one of more than 50 women who have accused Cosby of sexual assaults, some of them dating back decades.
His defence team says he denies all allegations and says any sexual encounters were consensual.