Issues related to fertility and pregnancy, once moot, are now extremely relevant to the care of a growing number of CF patients entering adulthood. With rare exception, men are infertile, due to the almost universal presence of malformations of the reproductive tract causing obstructive azoospermia. Emphasis in the care of these patients should be directed toward confirmation of infertility and counseling to allay anxieties. In contrast, a significant albeit unknown proportion of women are fertile and a steadily increasing number of these women are conceiving. The accumulated clinical experience has demonstrated that pregnancy is well-tolerated by patients with mild disease while associated with increased maternal and fetal complications in those with severe disease. In light of current uncertainties in accurately predicting outcome in all but the most clear-cut cases, the physician must exercise clinical judgment in providing a realistic assessment of the medical risks involved and of the advisability of pregnancy. This assessment should be based on a thorough and objective evaluation of the pulmonary, cardiac, and nutritional status of the patient. Future efforts, assisted by data collected for the national CF patient registry, should be directed toward better defining the long-term impact of pregnancy on the natural history of CF and more precisely defining the pregravid parameters useful in predicting outcome for both mother and child.