Introduction Although there are dierences in the conceptualization of the syndromes of attention±de®cit and overactivity between the International Classi®cation of Disorders, tenth edition ICD-10; 30) and the Diagnostic and Statistical Manual of Mental Diseases, fourth edition DSM-IV; 3), the authors have emphasized that the similarities are greater than the dierences 29). The DSM-IV uses the term attention±de®cit/hyperactivity disorder ADHD), while the ICD-10 utilizes the term hyperkinetic disorders to describe these syndromes. Independent of the terminology used, children and adolescents suering from these syndromes have impor- tant impairments in multiple domains 7). Recently, there is increasing concern about the persistence of symptoms and impairments even in adults 21, 28). Since the diagnostic continuity between child and adolescent ADHD is becoming well established 7), mental health professionals who deal with adolescents need to recognize potential patients with ADHD. The clinical version of the ICD-10 provides some guidelines for the diagnosis of hyperkinetic disorders, emphasizing that the symptoms must have an early beginning before the age of 6 years). The DSM-IV emphasizes ®ve main criteria for the diagnosis of ADHD: a) a pattern of inattention and/or hyperactivity/impulsivity symptoms that is maladaptive and inconsistent with developmental age; b) beginning of some symptoms causing impairment before the age of 7 years; c) presence of some impair- ment in, at least, two settings; d) clear evidence of clinical signi®cant impairment in social, academic or occupational functioning; and e) exclusion of other higher priority mental disorders that better explain the symptoms. Since the publication of the ICD-10, the DSM-IV and the DSM-IV ®eld trials for ADHD 19), there has been considerable debate about age-of-onset of impairment ORIGINAL CONTRIBUTION European Child & Adolescent Psychiatry 9:212±218 2000) Ó Steinkop Verlag 2000 L. A. Rohde J. Biederman H. Zimmermann M. Schmitz S. Martins S. Tramontina Exploring ADHD age-of-onset criterion in Brazilian adolescents Accepted: 22 February 2000 L. A. Rohde &) á H. Zimmermann M. Schmitz á S. Martins á S. Tramontina ServicËo de Psiquiatria da InfaÃncia e Ado- lesceÃncia Hospital de ClõÂnicas de Porto Alegre Rua Ramiro Barcellos 2350 Porto Alegre Rio Grande do Sul 90035-003 Brazil E-mail: lrohde@zaz.com.br Dr. J. Biederman Pediatric Psychopharmacology Unit, Mass. General Hospital Abstract Objective: To explore age- of-onset criterion for the diagnosis of attention±de®cit hyperactivity disorder ADHD) in a school sample of young Brazilian adolescents. Methods: 191 students aged 12 to 14 years were evaluated using DSM-IV ADHD criteria, measures of ADHD symptoms and global impairment. Results: Both adolescents with ADHD n 30) and adolescents who ful®lled all DSM-IV ADHD criteria, except age of onset of im- pairment criterion ADHD w/o age- of-onset, n 27) had signi®cantly higher scores on Attention Prob- lems, Delinquent and Aggressive Behavior scales of the Child Behav- ior Checklist CBCL) and lower scores on the Child Global Assessment scale CGAS) than non-ADHD adolescents n 134). Adolescents with ADHD and youths with ADHD w/o age-of-onset did not dier signi®cantly in any measure assessed. Conclusion: These results concur with recent literature proposing re- vision of the age-of-onset criterion for the diagnosis of ADHD. Key words Attention de®cit hyper- activity disorder ± hyperkinetic disorders, inattention ± hyperactivity