Parents and patients in the Rhode Island Cystic Fibrosis Center were interviewed to determine the extent of compliance with various aspects of the therapeutic regimen. Current patterns of compliance were compared with retrospective clinic records of reported compliance up to 8 years prior to the time of study. Actual clinic attendance and reported compliance with medications were high. Patients reported significantly lower compliance with diet and chest physiotherapy. Most patients reported less compliance with chest physiotherapy at the time of study than 3 to 8 years earlier, regardless of the severity of their lung disease. Patients frequently reported self-medication with non-prescribed vitamins, antibiotics, or other drugs. Patients' perceptions of the severity of their disease and the possible adverse consequences of discontinuing therapy probably contribute to both good medication compliance and self-medication.