ESTER-assessment is a new assessment instrument for youths (0-18 years), and includes 19 empirically-derived risk and protective factors for conduct problems. This study tests the inter-rater reliability of the five-point rating scale used to assess the 19 factors in ESTER-assessment on 30 institutionalized girls and their file information. Exact agreement between raters varied from 38 to 72 percent on the 19 individual factors, a result much better than chance. Intra-class correlations of the two independent raters on the majority of the 19 individual factors were fair to good. In conclusion, the results lend support to the inter-rater reliability of ESTER-assessment.