This study examined the relationship between early childhood risk factors for antisocial behavior and the monetary costs associated with criminal convictions for 379 clinic-referred boys. Participants were assessed using a structured risk assessment instrument, the Early Assessment Risk List for Boys (EARL-20B), intended for use with boys aged 6–11 with conduct problems. Criminal conviction data were used to calculate costs borne by victims, the correctional system, and other areas of the criminal justice system for participants between the ages of 12 and 20. For the total sample, the average cost per person was $580,181. Using the EARL-20B total score to derive quartile groups, the average lowest and highest risk quartile boys cost $361,581 and $878,460, respectively. Including estimates associated with undetected crimes increased per-person estimates to $1,058,854 and $3,536,441. For all risk groups, most of the costs occurred during mid-to-late adolescence, between the ages of 15–17. Analyses of individual EARL-20B items revealed that the three most expensive risk factors were manifesting antisocial attitudes ($920,657), poor coping ability ($768,416), and poor academic performance ($772,256). The results from this study show that it is possible to quantify childhood risk in monetary terms, and that substantial cost savings can be realized if developmental crime prevention programs are targeted at antisocial children before they reach the age of criminal liability. Psychologists play an important role in this pursuit by developing and using risk/needs assessment instruments, choosing and targeting interventions based on the results, developing new programs, training personnel, and evaluating the effectiveness of programs. (PsycInfo Database Record (c) 2021 APA, all rights reserved)