In this paper, the authors present the results of a study that compared two think-aloud usability testing methods: the concurrent think-aloud and the retrospective think-aloud methods. Data from task performance, testing experience and usability problems were collected from 30 participants equally distributed between the two think-aloud conditions. The results suggest that while the thinking aloud method had no impact on task performance and testing experience, participants using the concurrent think-aloud method reported a larger number of problems with the test interface than participants using the retrospective think-aloud method. These findings suggest a reason for preferring the concurrent think-aloud method to the retrospective one.