Healthy Families Arizona is a voluntary, home visitation program, aimed at the prevention of child abuse and neglect. This secondary prevention program is targeted to the parents of newborns with risk factors that make them vulnerable to child abuse and neglect, and at risk of parent/child relationship and child development problems. The risk factors that qualify parents for the program include parental history of abuse and neglect; substance abuse; mental health problems; poor coping skills; a lack of social support; unrealistic developmental expectations of infants and toddlers, difficulty with bonding and attachment; attitudes favorable toward harsh discipline; anger management issues; and a lack of resources to meet basic needs. Modeled on the Healthy Families America program, Healthy Families began in Arizona in 1991 with two sites. Administered by the Arizona Department of Economic Security, Healthy Families Arizona has realized considerable growth over the years, and is now available to families statewide. As with any considerable investment in cost and effort, the question of return is central to ongoing support of the Healthy Families Arizona program. Does the Healthy Families Arizona program (a) reduce the risk of child abuse and neglect; (b) lead to better health and development for children, and (c) does it enhance parent/child relationships? The longitudinal evaluation of Healthy Families Arizona was designed to answer these questions.