Studies on the inter-rater reliability on the Children's Global Assessment Scale (CGAS) and the Global Assessment of Psychosocial Disability (GAPD) involving different subgroups of 145 outpatients from 4 to 16 years of age showed fair to substantial intraclass correlations of 0.59 to 0.90. Raters of different training levels participated. Interrater reliability was dependent on number of ratings per rater, training, available data sources and experience. A more detailed description of anchor points resulted in higher inter-rater agreement by psychiatrists training in child and adolescent psychiatry, but did not influence the inter-rater reliability among more (widely) experienced raters. Both the CGAS and the GAPD seem to be sufficiently reliable tools in clinical practice. The CGAS seems to be more sensitive to inter-rater variation than the GAPD.