A search of the literature showed the lack of a suitable measure for assessing the impact of minor illness on children and their families. Such illness can lead to considerable disruption within the family and particularly to the parent primarily responsible for the care of the ill child. Discussion groups were run with parents who had a child who had had chickenpox within the previous 6 months. Analysis of the transcripts from the groups produced items indicating three types of disruption; parents' distress, changes in the behaviour of the ill child and general disruption to family arrangements. Items from the transcripts were formed into a questionnaire which was then used in a study of 61 families in which a child had become ill with chickenpox within the previous 7 days. The principal carer completed the measure every evening for a fortnight. The results of the study showed considerable disruption over the first few days of the child's illness, followed by a steady reduction over the whole 2-week period.(ABSTRACT TRUNCATED AT 250 WORDS)