The current study examined the predictors of parent-child relationship quality and developmental change in a sample of children adopted into the U.K. following severe early privation, and in a comparison sample of nondeprived, within-country adoptees. One hundred and fifty-eight children adopted from Romania and 52 U.K. adoptees were assessed at age 6 years; longitudinal data (age 4 and 6 years) were available on the 110 Romanian adoptees placed into U.K. homes before 24 months of age and all U.K. adoptees. Ratings of parent-child positivity and negativity during a semistructured interaction task were obtained from coders who were blind to the child's background. Results indicated that adoptive parent-child relationship quality was related to duration of deprivation and that cognitive/developmental delay mediated this association. The magnitude of this effect was modest and diminished over time. Longitudinal analyses revealed that positive change in parent-child relationship quality was most marked among children who exhibited cognitive catch-up between assessments. The direction of effects appeared to be primarily child to parent. The findings underscore the need for further research on the long-term impact of early experiences on psychosocial development.