The reliability and validity of the teacher version of the Child Symptom Inventory-4 (CSI-4) was examined in 248 boys referred for evaluation of behavioral and emotional problems. The CSI-4 is a behavior rating scale whose items correspond to the symptoms of DSM?IV-defined disorders. The results indicated satisfactory internal consistency reliabilities for most symptom categories, and CSI-4 scores converged and diverged in a theoretically consistent manner with respective scales of the Teacher's Report Form (Achenbach, 1991), the IOWA Conners Teacher's Rating Scale (Loney & Milich, 1982), and the Diagnostic Interview for Children and Adolescents--Revised Parent Version (DICA-P; Reich, Shayka, & Taibleson, 1991). Correlations between teacher and parent CSI-4 ratings were low to moderate, whereas all correlations between teacher ratings and child self report were very low ( rs < .16). Children who met DICA-P diagnostic criteria for attention-deficit/hyperactivity disorder, oppositional defiant disorder, and conduct disorder received significantly higher corresponding CSI-4 teacher symptom ratings than children not so diagnosed. Collectively, findings support the clinical utility of the CSI-4 in clinically referred boys.