Adolescent delinquency is costly at both the individual-level and the societal-level. Many conduct-disordered (CD) adolescents meet criteria for antisocial personality disorder (ASPD) in adulthood, and adolescent alcohol/substance use disorders (ASUDs) are associated with increased risk for adult antisocial outcomes. CD research and treatments have historically targeted boys, but recent efforts have explored the phenomenon of antisocial behavior in girls. However, few studies have assessed male/female differences in presentation and course of CD/ASPD in substance-disordered adolescents. In particular, no existing research has examined gender differences in antisocial behavior trajectories for substance-disordered youth through adolescence and into young adulthood. This study investigated the role of gender in longitudinal patterns of antisocial behavior in 424 adolescents (intake M age=16.2 years) from an existing project examining clinical course for ASUD youth. The sample was 50% female, 62% Caucasian, and intake age range was 13-18 years. Gender differences in CD/ASPD and ASUD symptoms and prevalence rates were assessed during initial treatment and 2, 4, 6, and 8 years post-treatment. Antisocial behavior trajectory groupings were established using general growth mixture modeling, and gender differences in trajectory classes were assessed. Conclusions are: (1) Gender differences in CD/ASPD symptoms and disorder prevalence rates were present during treatment and throughout the 8 years post-treatment. Boys had higher disorder prevalence, more total symptoms, more severe symptoms, and more symptoms independent of substance use; (2) ASUD prevalence was higher for boys at intake, 4, 6, and 8 years post-treatment. Gender differences in ASUD symptoms emerged in late-adolescence and early-adulthood, with female symptom levels higher at 2 years post-treatment then lower at 4, 6, and 8 years; (3) A five class solution ("late-escalating," "high-start desisting," "early-escalating," "gradual desisting," and "highest-start desisting" classes) was determined optimal based on model fit indices. Gender was related to CD/ASPD trajectory class membership with girls overrepresented in a "late-escalating" class and a "gradual-desisting" class. Boys were overrepresented in a "highest-start desisting class" and an "early-escalating" class. Overall, gender related findings indicate that despite lower rates of CD/ASPD compared to their male counterparts, substance-abusing girls are at risk for particular forms of antisocial psychopathology in late-adolescence and early-adulthood.