Chronic illness in childhood affects family functioning, and professional support is required when the child is being cared for at home The focus of concern for this study is the nursing contribution to the support of the family A longitudinal ethnographic study of the experience of four families caring for a child with cystic fibrosis provided data Analysis of the four case studies provides insight to the effect of cystic fibrosis on family interaction The genetic aspects and the life-threatening nature of the illness are seen to have a profound effect on the parents’ lives The experience of crisis and the chronic burden of care are described. The context of long-term care requires the nurse to share the illness trajectory with the families and to help family members to travel it together This is seen to require a high level of interpersonal skill and considerable emotional investment The issues for nursing are examined The research arose from practice, and it contributes to theoretical explanation of nursing interaction, and the relationship of systems thinking to understanding of the nursing situation The case for the development of family nursing practice to meet contemporary health care needs is argued