Hundreds of people showed up in cities across the globe to participate in International Pillow Fight Day 2013, officials said.
The eighth annual event had few rules, other than no hitting someone without a pillow and no feathered or zippered pillows allowed.
In Cambridge, hundreds of participants wielding pillows gathered in North Point Park and began swinging at 3 p.m.
John Fotheringham, who has attended four of the pillow fights in Montreal, told The (Montreal) Gazette the event is all about having a good time.
"It's fun," Fotheringham said. "It's held outside on a spring day. It's positive. And it has this energy bolstering feeling that is really good."
New Yorkers met in Manhattan's Washington Square Park to duke it out, WPIX-TV, New York, reported.
Pillows discarded at the New York City pillow fight were later donated to a homeless shelter.
In Washington, many participants dressed up, The Washington Post reported.
"It's a 'tee-hee' kind of thing," said pillow-fighter Jayne Mazzone, who wore a white tutu and red face paint for the event. "Everybody has a childish side."