Symptom burden is a key component of health-related quality of life in patients with cystic fibrosis (CF). To examine symptom prevalence and characteristics of adults with CF, we administered the Memorial Symptom Assessment Scale (MSAS), a previously validated measure of symptom burden, to CF patients enrolled in the Project on Adult Care in CF. The mean age of the 303 respondents (response rate 91%) was 32.8 years (range, 19-64); 58% were female, and their mean baseline pulmonary function (FEV(1) % predicted) was 69% (SD 28%). The median number of symptoms reported was 10, and there was no difference in the number of symptoms reported based on age, gender, or FEV(1). The most prevalent symptoms were cough (94%), shortness of breath (77%), and lack of energy (77%). Lack of energy and irritability caused the highest level of distress. MSAS symptom subscales were only moderately correlated with symptom status domains from existing CF health-related quality of life measures. Factor analysis led to the development of three distinct MSAS CF-symptom subscales, each with high internal validity. These findings show that adults with CF have a high symptom burden, particularly with respiratory and psychological symptoms, and that the new MSAS CF-specific subscales are a reliable measure of symptom distress in the CF population.