The present study was an attempt to contribute to the standardized assessment and the study of prevalence of problem behavior in children 2- to 3-years old by means of empirically derived rating scales. The basic questions were: 1. What are the psychometric characteristics of the Dutch version of the Child Behavior Checklist for Ages 2-3 (CBCL/2-3)? 2. What is the prevalence of problem behavior in Dutch toddlers aged 2-3 years in the connnunity, and in a broadly defined clinical sample as measured by the CBCL/2-3? 3. How are CBCL/2-3 scores in both samples related to demographic, family, and child characteristics, and in the clinical sample also to clinically relevant variables, such as referral complaints and psychiatric diagnosis? 4. How predictive are CBCL/2-3 scores of behavioral/emotional problems at home and at school over a 2-year interval, as measured by parents' and teachers' standardized ratings of problem behavior. and reports of significant problems at home and school? 3