Do you use hot or cold water when you wash your hands?
Well, new research suggests that cold water might be just as good as warm water!
US scientists studied a group of volunteers and found that washing with cold water (15C) instead of hot water (38C) didn't make a big difference to how much bacteria was killed.
Washing your hands regularly is really important to stop the spread of germs, which can make you ill.
The team at Rutgers University looked at different things, like using more or less soap, to see whether they affected how effective hand washing was.
They also said that using antibacterial soap instead of normal soap didn't make much difference either.
But they did say that you should scrub your hands for at least 10 seconds.