We examined whether patients with cystic fibrosis, a chronic illness, take pancreatic enzymes in the manner recommended by physicians. Administration by other means could lead to costly, risky, potentially unnecessary medical interventions. Families of patients with cystic fibrosis were surveyed during routine clinic visits over a 6-month period. Nine of 47 patients (19%) were found to be taking enzymes in a manner not recommended or suspected by physicians, exclusively after meals. There was a trend for these patients to be more likely to be taking unusually high doses of these expensive enzymes. Only 25% had specifically discussed enzyme administration with caregivers within the previous 6 months. Health care providers may be disturbingly unfamiliar with their patients' practices, which could have significant consequences. Therefore, medical personnel need to regularly review all aspects of their patients' care in detail.