Findings concerning the psychometric quality of the German version of the Teacher-SDQ (T4-16-SDQ) are presented. This questionnaire was used with a sample of children aged three to five years as part of the Augsburg Longitudinal Study for the Evaluation of the Prevention Programme Papilio (ALEPP). The dimensional structure of the questionnaire could be replicated excellently using a factor analysis with varimax rotation. Only two items exhibit ancillary loadings exceeding .40. The internal consistency (Cronbach’s Alpha)is satisfactory and varies between = .73 and = .86. Overall, using the British critical values for ‘prosocial behavior’ by two points and to raise those for the problem scales (except for ‘Emotional Symptoms’) by one point. Age effects appear for the subscale ‘Hyperactivity’ as well as for the ‘Total Difficulties Score’, while gender effects are found for all subscales except ‘Emotional Symptoms’. According to these results, the SDQ is recommended as an economical and practical instrument for the assessment of young children’s behavior.