We measured acceptance of carrier testing for cystic fibrosis in the community when offered in a primary care setting, determined variables influencing acceptance, and assessed knowledge of cystic fibrosis 3-6 months later. A total of 5,102 individuals age 18-50 years attending general practices or a family planning clinic in Western Australia completed questionnaires about knowledge of cystic fibrosis and the State Anxiety Inventory. Testing for the delta F508 gene was offered. After 3-6 months, carriers, a sample of consenting participants who were not tested, and a sample of test-negative participants were sent a further questionnaire; 43.5% of participants chose to be tested for cystic fibrosis carrier status. Women, younger people, people with higher education, people without children, and people planning to have children were more likely to be tested. After 3-6 months, carriers gave correct responses to questions about cystic fibrosis more frequently than those who tested negative or were not tested; 82.2% of carriers knew that they were definitely a carrier and 31.1% of test-negative individuals believed they were definitely not carriers. Thus, population carrier screening for cystic fibrosis offered in a community setting in Western Australia was acceptable to almost half of those offered testing, particularly younger people and those planning to have children, for whom knowledge of carrier status could be useful in making reproductive decisions. There was evidence that tested individuals recalled information in a way that minimised their risk of being a carrier.