A 12-year-old is very ill in hospital after hitting a car when he was crossing the road in his Heelys.
The boy, from East Sussex, needed an operation after the accident. It comes after several kids contacted Newsround with safety worries about Heelys.
Heelys look like trainers, but they have wheels in the heels which turn them into skates. They were on many wish lists this Christmas.
It's not clear if the injured boy was skating at the time of the accident.
Experts have been encouraging kids to wear protective gear when they are using their Heelys, which usually cost between £50 to £100.
Ten-year-old Newsround viewer Thomas emailed us with his concerns about the shoes.
"I think they are dangerous and anti-social as well as being highly over-priced," he said.
"Someone at my school has broken her ankle. Should there be an age restriction? Are they dangerous? Should shops ban them? Will this craze last?"
One of the biggest sellers of Heelys - a company called Totally Phat - responded to Thomas's questions.
It said it had clear safety guidelines and staff had been trained to teach kids how to use Heelys.
It also said that it recommended that parents insisted that kids wear safety equipment, such as wrist, knee and elbow pads as well as helmets.
Meanwhile, health officials in Northern Ireland have launched an investigation to try to find out just how many Heelys-wearing kids are getting hurt.
If you have had a Heelys accident, tell us about it by clicking on the link on this page.