While developmental perspectives on sexual violence have gained much interest in recent years, few empirical studies have been conducted to better understand its origins. This study attempts to fill this gap by examining the onset of physical aggression and normative sexual behaviors in preschoolers. This study is based on a sample of at-risk children (n = 100) recruited as part of the KD-BEAR project, an on-going longitudinal study conducted in Vancouver, British Columbia, Canada. Semi-structured interviews were completed with the primary caregiver and the child. The structural model examined showed a significant and important latent correlation between physical aggression and sexual behaviors across models tested, after controlling for child and familial characteristics. Furthermore, findings showed that male preschoolers coming from low income families having been referred for assessment and/or treatment for an externalizing spectrum disorder showed higher levels of both aggression and sexual behaviors. The implications of these findings are discussed in light of developmental models of sexual violence, and the secondary prevention of sexual violence at its earliest stages. Copyright © 2010 John Wiley & Sons, Ltd.