The biological concomitants of childhood conduct disorder (CD) have seldom been considered separate from those of hyperkinesis with which CD is often comorbid. CD predicts an increased likelihood of developing a personality disorder and is often associated with an antisocial outcome. Childhood CD may originate in a stressful upbringing in a dysfunctional family environment, and has been reported to be associated with unusual physical or sexual development and thyroid dysfunction. Methods: We therefore explored circulating levels of hormones from adrenal, gonadal and growth-hormone axes associated with stress, aggression and development in 28 CD patients and 13 age-matched healthy children (10-18 years old). Results: 1/ The CD group had higher levels of dehydroepiandrosterone sulphate (DHEA-S) and corticotropin (ACTH) and for those under 14 years of age there was more free triiodothyronine (fT3) in the circulation. 2/ There were no differences for gonadal hormones, and neither the levels of steroid hormones nor the ratings of maturity (early/late) were associated with aggression, as has been reported elsewhere. 3/ Smaller physical measures in CD children correlated with DHEA-S and growth factors (e.g. IGF-I): 4/ increased ACTH and fT3 correlated with restless-impulsive ratings, and DHEA-S with 'disruptive behaviour'. Conclusions: Imbalances in the adrenal and growth axes may indeed have neurotrophic repercussions in growth and development.