OBJECTIVE: To determine the extent to which the reported variations across countries in the prevalence of attention-deficit hyperactivity disorder are due to cultural differences among raters, the authors examined the degree to which mental health professionals in four countries differed in their ratings of hyperactive-disruptive behaviors in children. METHOD: Mental health professionals from China (N = 8), Indonesia (N = 12), Japan (N = 9), and the United States (N = 8) rated the presence and degree of hyperactive-disruptive behaviors in standardized videotape vignettes of four 8-year-old boys participating in individual and group activities. RESULTS: Chinese and Indonesian clinicians gave significantly higher scores for hyperactive-disruptive behaviors than did their Japanese and American colleagues. CONCLUSIONS: These findings suggest that perceptions of hyperactivity vary significantly across countries even if uniform rating criteria are applied. Without correction for these perceptual differences, cross- cultural prevalence rates of hyperactivity may not be comparable.Abstract Teaser