This paper presents an updated cost-benefit analysis of the High/Scope Perry preschool Program, using data on individuals aged 40. Children were randomly assigned to a treatment or control group. Program costs are compared against treatment impacts on educational resources, earnings, criminal activity, and welfare receipt. Net present values are calculated for participants, the general public, and society. The treatment group obtains significantly higher earnings. For the general public, higher tax revenues, lower criminal justice system expenditures, and lower welfare payments easily outweigh program costs; they repay $12.90 for every $1 invested. However, program gains come mainly from reduced crime by males.