Objective To predict teen-age arrests from measures of childhood defiance in attention-deficit hyperactivity disorder (ADHD) boys. Method Defiance ratings that were independent of hyperactivity were obtained on two groups of ADHD boys. Official arrest data obtained on all subjects 9 years later were used as the outcome measure. Results ADHD boys with high defiance ratings had significantly higher felony offender rates than did boys with low ratings. However, the ADHD boys with low ratings had significantly higher felony offender rates than did normal control boys. Conclusions Clinicians and parents should be alerted to the fact that minor antisocial features in ADHD boys, such as defiance, signal an increased risk for later serious antisocial behavior. However, they should not be misled by the absence of defiance in ADHD boys to think that these boys are not at risk for serious antisocial behavior (arrests for serious criminal behavior) later in life.