The rate of technical advance in genetics contrasts sharply with the slow diffusion of information on this subject to the general population. In this paper, we investigate the initial knowledge about cystic fibrosis of a group of adults with increased interest in psychosocial issues, but with no special pre-existing knowledge or training in genetics. Attitudes towards carrier screening and prenatal diagnosis for CF were also evaluated, after brief written information had been given on this disease. We found that the studied group had only a poor knowledge of the nature of CF and an even more limited awareness of its inheritance. This knowledge was mainly associated with educational level. Most respondents had no objections to population-wide carrier screening for CF, at least if the test was proposed and not systematically imposed by the government. It is striking that a smaller proportion were interested in knowing their own carrier status. The majority of the group were in favour of prenatal diagnosis for CF. Factors associated with knowledge and attitudes are described. In the discussion, special attention is paid to the psychosocial complexity of mass screening.