While descriptions of the effects of chronic childhood illness on the family appear in the literature, there have been few attempts to develop a formal measure of this impact. As part of a longitudinal study of chronic illness in childhood, the development of a measure was undertaken. The conceptual framework and methodology employed in scale development are described. A 24-item scale is presented which elicits variability in response and which is internally consistent. A factor analysis reveals that 4 dimensions of impact are contained in the measure: Financial, Social/Familial, Personal Strain, and Mastery. Psychometric data were derived from administration of the instrument to 100 mothers of chronically ill children. The potential usefulness of the scale in health research is discussed.