Kids who stammer should get help to sort out the problem before they go to school, according to researchers.
They tested out a new treatment on 54 kids aged two to six and found that it really made a difference.
The children following the treatment reduced their stammering by 77% compared to 43% who didn't do it.
Around 80% of kids who stammer recover from it naturally and there has been an argument that treatment doesn't help but this seems to prove otherwise.
About one in 20 children develop a stammer.
The researchers said the new treatment became less effective once kids had reached school age.
They say that delaying the treatment puts children at risk of experiencing "the disabling effects of... stuttering throughout life".