Hundreds of naked cyclists pedalled through London and Brighton at the weekend as part of the World Naked Bike Ride.
About 700 cycled through central London after more than 200 rode through Brighton, reports the BBC.
The naked cyclists - and others with strategically-placed body paint, sticky tape or bum bags - were highlighting the damage caused by car dependency.
They were also promoting the environmental benefits of cycling.
The World Naked Bike Ride is now in its fourth year with more than 60 cities participating in 2007.
The London leg began at Hyde Park and finished in Wellington Arch, a route of about six miles.
Naked cyclist Martin Ireland said: "We are seeing an increasing number of stories of melting ice caps and Antarctica crumbling away and no government is doing anything serious about this.
"They are paying lip service to the problem so people have been taking to their bikes, unclothing, to express their feelings about it."
Duncan Blinkhorn, 45, one of the organisers of the seven-mile Brighton ride, said: "This is a fun if outrageous way to make the serious point that we should not have to tolerate roads, cities and a planet dominated by the brutishness of cars that routinely foul the air we all breathe.
"Bikes and naked bodies harm nobody. Car fumes are driving us all to climate chaos."