Current widespread use of the same youth assessment measures and scales across different nations assumes that youth psychopathology syndromes do not differ meaningfully across nations. By contrast, the authors' syndromal sensitivity model posits 3 processes through which cultural differences can lead to cross-national differences in psychopathology syndromes. The authors tested this model in a comparison of Child Behavior Checklist syndromes for adolescents in Thailand and the United States. In support of the model, about half of the Thai-U.S. syndrome comparisons showed poor agreement (kappa = 0.40), and distinctive Thai syndromes emerged reflecting 3 prominent themes in Thai research literature: delayed maturation, indirect aggression and/or delinquency, and sex problems in boys. Such syndromal dissimilarity carries significant implications for assessment, diagnosis, epidemiology, and intervention across national boundaries.