Objective: To test the ability of a 3-item screening tool (Parenting Responsibility and Emotional Preparedness [PREP]) to detect adolescent mothers at elevated risk for nonoptimal parenting and poor child development outcomes at 2 years of age. Design: A4-site prospective cohort study conducted from December 2001 to August 2007 of adolescent mothers recruited in the third trimester of pregnancy and followed up at 4, 8, 18, and 24 months post partum. Setting: Community clinics and home settings in Birmingham, Alabama; Kansas City, Kansas and Missouri; South Bend, Indiana; and Washington, DC. Participants: A total of 270 first-time adolescent mothers (aged 15-19 years) and their infants (birth to 2 years of age). Main Exposures: Naturalistic observations of parentchild interactions and quality of home environment during the first 2 years of life. Outcome Measures: Maternal mental health and cognitive indicators, positive mother-child interactions, quality of home environment, child social-emotional development, and child cognitive development (Bayley scales). Results: PREP scores identified adolescent mothers with significantly elevated depressive symptoms and childhood trauma and lower scores of knowledge of infant development and maternal IQ. PREP predicted significantly lower quality of home environments and higher levels of nonoptimal mother-child interactions at 4, 8, and 18 months. PREP also predicted significantly lower child outcomes at 2 years of age for cognitive scores and higher levels of depressive and withdrawal symptoms and dysregulation and negative emotionality. Conclusions: PREP is a low-cost, easily administered, nonstigmatizing screening tool that identifies adolescent mothers who self-recognize that they need help to meet their infants' social, emotional, and cognitive needs. ©2012 American Medical Association. All rights reserved.