Using the ICD-10 criteria for mental and behavioral disorders, a series of five written case-histories was rated by 32 clinicians with various training backgrounds and different degrees of clinical expertise. As expected, reliability was dependent on clinical expertise and increased when an option for an alternative diagnosis was provided in addition to the main diagnosis. Inter-rater agreement in 10 written case-histories rated by senior child and adolescent psychiatrists was to 66%. In comparison with previous studies based on the ICD-9, there is some evidence that the improved conceptualization of the ICD-10 contributes to better reliability.