This report provides an overview of the Colorado Adoption Project (CAP), a longitudinal, prospective, multivariate adoption study of behavioral development. Examples of the types of analyses that can be conducted using this design are presented. The examples are based on general cognitive-ability data for adoptive, biological, and control parents; assessments of their home environment; and Bayley Mental Development Index scores for 152 adopted children and 120 matched control children tested at both 1 and 2 years of age. The illustrative analyses include matched control children tested at both 1 and 2 years of age. The illustrative analyses include examination of genetic and environmental sources of variance, identification of environmental influence devoid of genetic bias, assessment of genotype-environment interaction and correlation, and analyses of the etiology of change and continuity in development.