Cystic fibrosis, which is one of the most common autosomal recessive disorders, has a carrier frequency of approximately 1 in 25 among whites in the United States. In this population approximately 75% of the mutations in patients with cystic fibrosis correspond to a 3 base pair deletion that results in the loss of a phenylalanine residue at amino acid position 508 (designated delta F508) from the coding region of the cystic fibrosis gene. Currently, only about half of the couples at risk can be identified as cystic fibrosis carriers. We support conclusions of the National Institutes of Health Workshop on Population Screening for the Cystic Fibrosis Gene, which state that carrier testing should be offered to all individuals or couples with a family history of cystic fibrosis. Good science and solid educational and counseling strategies must be in place before screening for cystic fibrosis is routinely offered to those with a negative family history. Pilot programs that investigate research questions in the delivery of population screening for cystic fibrosis carriers are urgently needed.