Objective: To test the hypothesis that US clinicians diagnose prepubertal mania more commonly than UK clinicians. Methods: Five vignettes were presented to 73 UK clinicians and 85 US clinicians. Four cases represented complex scenarios where the diagnosis of mania was thought to be controversial, and one case was a 'classical' case of mania in an older child where it was thought there would be good agreement. Clinicians were asked to determine symptoms of mania, and their preferred diagnoses. Results: As predicted, overall there were significantly more diagnoses of mania in the US than the UK (P ≤ 0.0001). US clinicians were significantly more likely to diagnose mania in three of the four complex cases, and there was good agreement in the case of classical mania. In addition, UK clinicians were significantly more likely to diagnose pervasive developmental disorders and adjustment disorders, whereas obsessive compulsive disorder was more commonly diagnosed in the US. Conclusion: There may be differences in how clinicians in the US and UK interpret mania-like symptoms in younger children, which may have implications for diagnosis and management. © 2007 Steinkopff Verlag Darmstadt.