Story stem measures allow the assessment of children's representations of relationship functioning, but are expensive and time-consuming to administer. We developed a computerized story stem measure which does not require specific training for administrators and which allows the child to produce their own animated, narrated story completion. This paper describes, firstly, the reliability of the Computerized MacArthur Story Stem Battery (CMSSB) and, secondly, a preliminary comparison of children in foster care and school controls on narrative coherence, intentionality and avoidance. The CMSSB showed good inter-rater reliability. A group of children in foster care showed significantly poorer coherence of narrative, less intentionality and greater avoidance on the CMSSB compared to a school comparison group. Copyright © 2006 John Wiley & Sons, Ltd.