There is a robust association between prenatal smoking and disruptive behavior disorders, but little is known about the emergence of such behaviors in early development. The association of prenatal smoking and hypothesized behavioral precursors to disruptive behavior in toddlers (N=93) was tested. Exposed toddlers demonstrated atypical behavioral patterns, including (1) escalating externalizing problems from 18 to 24 months and (2) observed difficulty modulating behavior in response to social cues. Specification of exposure-related behaviors is a first step toward generating testable hypotheses about putative mechanisms of effect. While it remains unclear whether prenatal exposure plays an etiologic role in the emergence of disruptive behavior, atypical exposure-related behavioral patterns are evident in the first years of life and demonstrate developmental coherence.