Children prenatally exposed to cocaine may be at elevated risk for adjustment problems in early development because of greater reactivity and reduced regulation during challenging tasks. Few studies have examined whether cocaine-exposed children show such difficulties during the preschool years, a period marked by increased social and cognitive demands and by rapid changes in reactivity and regulation. The authors addressed this question by examining frustration reactivity and regulation of behavior during a problem-solving task in cocaine-exposed and-unexposed preschoolers. Participants were 174 4.5-year-olds (M age = 4.55 years, SD = 0.09). Frustration reactivity was measured as latency to show frustration and number of disruptive behaviors, whereas regulation was measured as latency to approach and attempt the problem-solving task and number of problem-solving behaviors. Results indicated that cocaine-exposed children took longer to attempt the problem-solving task but that cocaine-exposed boys showed the most difficulties: They were quicker to express frustration and were more disruptive. Effect sizes were relatively small, suggesting both resilience and vulnerabilities.