BACKGROUND: Research on the cost of care of patients with cystic fibrosis is scarce. The aim of this study was to estimate the costs using age-specific medical consumption from real patient data. METHODS: The age-specific medical consumption of patients with cystic fibrosis in The Netherlands in 1991 was estimated from a survey of medical records and a patient questionnaire. A distinction was made between costs of hospital care, hospital and non-hospital medication, and home care. Costs per year were obtained by multiplying the yearly amount of care and the costs per unit. RESULTS: On average the annual cost of a patient with cystic fibrosis in 1991 was 10,908 pounds (hospital care 42%, medication 37%, home care 20%). The cost of care of cystic fibrosis in The Netherlands, with approximately 1000 patients, is estimated at 10.9 million pounds per year, which is 0.07% of the total health care budget. The cost of care of a patient up to the age of 35 is estimated at 614,587 pounds. When year-to-year survival is taken into account and future costs are discounted to the year of birth with a yearly discount rate of 5%, the cost of care of a patient with cystic fibrosis is estimated at 164,365 pounds for 1991. This estimate will be used in a prospective evaluation of screening for cystic fibrosis carriers. CONCLUSIONS: The cost of care of patients with cystic fibrosis estimated by age-specific medical consumption of real patients is higher than that estimated by non-age-specific medical consumption and/or expert opinions.