Effortful control is comprised of regulatory processes that are dynamically organized in real time to achieve situational and interpersonal goals. Yet, we know little about how the levels of children's effortful control change over a relatively short span of time and what implications such patterns may have for children's adjustment. In the present study, individual differences in preschoolers' effortful control processes during a cognitively challenging task were examined using a latent class growth analysis. Child and family risk factors were included in the model as potential predictors of different effortful control profiles. Concurrent and longitudinal associations between effortful control profiles and externalizing behavior problems also were explored. Participants were 235 children (113 girls) at elevated risk for conduct problems. Mother-child dyads were assessed for the child's effortful control and the mother's emotional and behavioral responsiveness via a videotaped, challenging block design task completed at home when children were 3 years old. Parents and teachers reported on child externalizing problems at the ages 3, 6, and 10 years. Child gender, child IQ, and family socioeconomic status were also incorporated in the analysis. Our analysis revealed three distinct patterns of changes in child effortful control during the block task: high-persistence (58%), declining persistence (14%), and low-persistence (28%). In each trajectory, child characteristics predicted the initial levels of effortful control whereas maternal behavioral responsiveness was associated with the maintenance of effortful control throughout the task. High- and low-persistence profiles were differentiated by child IQ and maternal behavioral responsiveness in the expected directions. Children in the three identified classes showed different levels of aggressive behavior during the block task. Furthermore, boys in the high-persistence class exhibited higher levels of externalizing behavior problems on teacher-ratings than those in the low-persistence class at ages 6 and 10. Generally, the identified effortful control profiles did not show significant relations to externalizing problems in girls, a finding that suggests gender-differentiated developmental pathways to externalizing behaviors. Results are discussed with respect to the value of microanalyses of children's early effortful control behaviors for prevention of externalizing behavior problems.