The first test screening of Harry Potter and the Prisoner of Azkaban took place in America last weekend.
Studio insiders at Warner Brothers confirmed to Newsround Online that the preview took place on 23 February.
The movie's director, Alfonso Cuaron, was in the audience at the Chicago cinema to see how fans reacted.
A review from the screening has already appeared on a film gossip website. It said that the film was "a huge improvement over the first two films".
It also described Emma Thompson's Professor Trelawney as "hilarious", although the review said that the special effects weren't all finished.