There are few data on the biological correlates of female antisocial behavior. This study compared adrenal androgen and gonadal hormone levels in adolescent girls with conduct disorder (CD) to girls without any psychiatric disorder (NC). We studied 87 girls, (47 CD; 36 NC), ages 15-17 years, obtaining three blood samples, drawn 20 min apart between 8 and 9 AM in the first 72 h of the onset of menstrual flow. Plasma was assayed for testosterone, estradiol, androstenedione, dehydroepiandrosterone (DHEA), dehydroepiandrosterone-sulfate (DHEA-S), sex hormone binding globulin (SHBG), and cortisol; area under the curve (AUC) for each of the three samples was used in the data analysis. We also calculated the Free Testosterone Index, Free Estrogen Index, Index of Hyperandrogenism and cortisol to DHEA ratio. In addition to receiving a full psychiatric interview, each girl completed a self-report questionnaire on general aggression. Main hormone analyses controlled for potentially confounding variables such as psychiatric comorbidity and race. Girls with CD had significantly lower cortisol to DHEA ratios, but did not differ from NC girls on any other hormone variable. Girls with symptoms of aggressive CD had significantly higher mean free testosterone indexes, lower SHBG levels, and lower cortisol to DHEA ratios than girls with non-aggressive CD. Girls with CD scored higher on the aggression questionnaire, but there was no association between general aggression and any hormone variable for the sample. Our data suggest that girls with CD, particularly aggressive CD, have lower cortisol to DHEA ratios, higher levels of free testosterone, and lower levels of SHBG. Clinical and research implications of these findings are discussed.