An interview and questionnaire were used to investigate the sexual functioning of married patients with cystic fibrosis. Only 20 percent of patients older than 19 years were married. Nine of the 30 married patients had serious sexual problems. Although these problems were all manifested as decreased desired, they had diverse causes; five of the nine were attributed to the CF. Some patients function quite well sexually, even in the face of severe disease. Physicians can assure adult CF patients contemplating marriage that they have a reasonable chance for normal sexual functioning.