Recent research has suggested that the presence of significant levels of callous-unemotional (CU) traits designates a clinically important and etiologically distinct subgroup of children and adolescents with serious conduct problems. Based on this research, CU traits have been included in the most recent revision of the Diagnostic and Statistical Manual of Mental Disorders – 5th Edition (DSM-5; American Psychiatric Association, 2013) – as a specifier for the diagnosis of conduct disorder. In this review, we attempt to understand CU traits within a developmental psychopathological framework. Specifically, we summarize research on the normal development of the prosocial emotions of empathy and guilt (i.e., conscience) and we illustrate how the development of CU traits can be viewed as the normal development of conscience gone awry. Furthermore, we review research on the stability of CU traits across different developmental periods and highlight factors that can influence this stability. Finally, we highlight the implications of this developmental psychopathological framework for future etiological research, for assessment and diagnostic classification, and for treatment of children with serious conduct problems.