With improved survival and new therapies for people with cystic fibrosis (CF), updated information on medical care expenditures for those individuals is needed. We estimated medical care expenditures, including both insurance reimbursements and patient out-of-pocket expenses, for privately insured people with CF and investigated how those expenditures varied with certain complications of CF. From a private insurance claims database of people covered by health plans associated with large corporate employers, we identified people with CF who were currently receiving medical care for the disorder and characterized their medical expenditures during the period 2004-2006. We selected a matching group of people who did not have CF based on age, sex, and geographic area, and calculated incremental expenditures associated with CF. We also examined the effect of age and certain complications of CF on these expenditures. The annual medical care expenditure for a person with actively managed CF averaged $48,098 in 2006 dollars, which was 22 times higher than for a person without CF. This ratio is high relative to other chronic disorders. Outpatient prescription medications made up the largest component of total expenditures for people with CF (39%). Those who were recorded in claims data as having a liver or lung transplant, malnutrition, diabetes, or a chronic Pseudomonas aeruginosa pulmonary infection incurred much higher expenditures than people without these conditions. People with CF will incur high medical expenditures throughout their lifespan. These findings will assist in the development of economic evaluations of future CF screening and management initiatives.