A cross-sectional survey of 60 families with a child with cystic fibrosis was undertaken to assess how much family members wanted to be told about the illness, to determine specific information needs concerning selected medical and psychosocial topics, and to determine whether this information had been provided in the past. Self-administered index measures were designed for this purpose. Most family members wanted complete and comprehensive information about cystic fibrosis. A minority of family members claimed they had not received basic medical information. Fathers and siblings wanted more medical information than mothers and patients. The majority of parents and patients wanted a great deal more information on the possible effects of cystic fibrosis on the patient's career, social life, marriage, and reproductive capacity. In general, family members had been given more medical than psychosocial information. Index measures were independent of the effects of patients' age, Shwachman score, and period since diagnosis. Social class was significantly associated with fathers' index measures of their specific information needs and information not given previously.