This study examined stability and malleability in the callous-unemotional (CU) traits of young boys (M age = 6.29 years, SD = 1.55) referred to clinics with conduct problems who underwent a parent-training intervention. In contrast to the high stability predicted, CU scores dropped posttreatment for a subset of the sample. However, as hypothesized, posttreatment and 6-month follow-up measures of CU traits and general conduct problems were predicted by different variables. Post hoc analyses of cases grouped according to pattern of CU stability indicated that boys with the most stable high CU traits showed the poorest outcomes at follow-up.