The objective of this study was to examine the validity of the Child Behavior Checklist (CBCL) Posttraumatic Stress Disorder (PTSD) subscale to screen for PTSD in children attending an inner-city early childhood mental health center. Using various measures, we assessed 51 preschool-age children with high exposure to trauma receiving outpatient child-parent psychotherapy for PTSD. We compared 15 items on the CBCL, a proposed subscale indicative of PTSD, to the UCLA-PTSD Index and to clinical diagnosis based on the Diagnostic and Statistical Manual of Mental Disorders (4th ed.; DSM-IV; American Psychiatric Association, 1994) and the Diagnostic Classification of Mental Health and Developmental Disorders of Infancy and Early Childhood (rev. ed.; DC:0-3; Zero to Three, 2005). Using the DC:0-3 criteria, 24% of the children were diagnosed with PTSD, but only 4% using the DSM-IV. The CBCL-PTSD subscale did not reach significant sensitivity or specificity to be a valuable screening tool for PTSD in this population.