Conduct disorder (CD) symptoms often emerge during the preschool years, but it is not clear whether they predict later symptoms. The present study examined whether age 3 CD symptoms predict age 6 CD symptoms beyond oppositional defiant disorder (ODD) and attention-deficit/hyperactivity disorder-hyperactive/impulsive (ADHD-HI) symptoms. Participants were 216 preschool children (M Age  = 44.19 months), including an externalizing sample (n = 161) and a comparison group (n = 55). Parents were administered a diagnostic interview when children were 3 years old and again 3 years later. The externalizing sample exhibited more CD symptoms than the comparison sample. In the externalizing sample, initial CD symptoms predicted later CD symptoms above and beyond ODD and ADHD HI symptoms; this relation was stronger for boys than for girls. Stealing, property destruction, and fighting independently predicted later CD symptoms. CD symptoms also predicted subsequent ADHD HI symptoms and predicted ODD symptoms at a level that approached significance. Results support the predictive validity of CD symptoms in preschool.