Severe behavior problems among people with intellectual and developmental disabilities (IDD) are a major barrier to integration in the community. Recent research suggests that these behaviors often begin very early in life and might be prevented by early identification and intervention (Rojahn, Schroeder, & Hoch, 2008). The current article presents a method of mass screening for early signs of severe behavior problems among infants and toddlers in Peru. A Parental Concerns Questionnaire (PCQ), which asks 15 questions, each related to a risk factor for severe behavior problems, based on past research on IDD, was used by veteran parents to interview 341 new parents who had been solicited by TV, radio, and public service announcements across the country. Of these, 262 were recruited and enrolled in a longitudinal study in which they will be followed for 12 months to see if at-risk children actually will develop severe behavior problems. An extensive initial interdisciplinary evaluation was given to each child. Consumer satisfaction questionnaires were given to the parents as to their attitude toward the screening method. Data from the vaccines contributedEvaluations of the sample suggest a very high hit rate (96%) by the screening instrument (PCQ). Consumer satisfaction was 98%, suggesting that the method was tolerated well by parents. The PCQ is a brief and efficient method to screen infants and toddlers at risk for severe behavior problems. The data also suggest that parents suspect these problems at a very early age. Early intervention thus seems a feasible strategy to intervene before these problems become deeply ingrained as children develop. (Contains 3 tables and 4 figures.)