<p>Callous-Unemotional behaviors (CU) can be seen in early childhood and are associated with negative developmental outcomes. The present study examined the genetic and environmental influences on the development of CU in the preschool period from both rank-order stability/instability and absolute-level developmental trajectories perspectives. A community sample of 310 twin pairs (MZ = 123; DZ = 187; 51% female) was longitudinally assessed with the Child Behavior Checklist 1¹/₂–5 reported by primary caregivers at ages 3, 4 and 5 years. Genetic and environmental contributions to rank-order stability/instability and absolute-level change in CU over time were assessed via biometric trivariate Cholesky and latent growth curve models, respectively. Age-to-age rank-order stability in CU was moderate and was mostly explained by genetic influences, whereas instability was due to genetic and nonshared environmental influences. Absolute-level change at the group level showed an overall pattern of decreasing CU across age, and individual differences in patterns of change were primarily due to nonshared environmental influences. Although rank-order change in CU was explained by genetic and nonshared environmental factors, within-individual changes in levels of CU were primarily influenced by nonshared environmental factors. These latter findings affirm that environmentally based intervention strategies in early childhood could affect CU trajectories.</p>