This article reviews evidence on the reliability and validity of the Children's Behavior Questionnaire (CBQ), and presents CBQ data on the structure of temperament in childhood. The CBQ is a caregiver report measure designed to provide a detailed assessment of temperament in children 3 to 7 years of age. Individual differences are assessed on 15 primary temperament characteristics: Positive Anticipation, Smiling/Laughter, High Intensity Pleasure, Activity Level, Impulsivity, Shyness, Discomfort, Fear, Anger/Frustration, Sadness, Soothability, Inhibitory Control, Attentional Focusing, Low Intensity Pleasure, and Perceptual Sensitivity. Factor analyses of CBQ scales reliably recover a three-factor solution indicating three broad dimensions of temperament: Extraversion/Surgency, Negative Affectivity, and Effortful Control. This three-factor solution also appears to be reliably recovered in ratings of children in other cultures (e.g., China and Japan). Evidence for convergent validity derives from confirmation of hypothesized relations between temperament and socialization-relevant traits. In addition, parental agreement on CBQ ratings is substantial. The CBQ scales demonstrate adequate internal consistency, and may be used in studies requiring a highly differentiated yet integrated measure of temperament for children in this age range.