We identified 124 carriers among 4,879 patients of prenatal care providers in the Rochester region. Six factors were identified that together permitted a correct classification regarding test acceptance for 77.5% of all subjects. For those pregnant, the most influential of these factors was a more accepting attitude toward abortion. As an indication for abortion, cystic fibrosis (CF) ranked between mild and moderate mental retardation. Of the 124 carrier women identified, we obtained 1-year follow-up information on 100. Mean score for CF knowledge at 1 year (77.4 +/- 13.2%), although significantly lower than immediately after counseling (84 +/- 12.4%), was still significantly higher than after detection but before counseling (51.1% +/- 20.7%). Anxiety about having a child with CF significantly declined from 25.8 +/- 8.0 SD immediately after counseling to 18.9 +/- 7.8 at 1 year (Spielberger State Anxiety Scale). Although 15 carriers regretted having been tested, 83% believed that they benefited from testing, 83% would make the same decision to be tested over again, and 79% would recommend testing to a friend. We conclude that, for most women, CF carrier screening accomplished its purpose: most carriers detected came for counseling, had their partners tested, and, if their partners were also carriers, had prenatal diagnosis. The major undesirable outcomes were that many women testing negative did not understand that a negative result did not exclude being a carrier and that three women found to be carriers did not have their partners tested because of anxiety or the unacceptability of pregnancy termination and therefore may not have carefully considered their decision to be tested. Both of these undesirable outcomes could have been avoided by greater attention to pretest patient education by the primary care provider.