Purpose: Guidelines recommend that genetic reports should be clear to nonspecialists, including patients. We investigated the feasibility of creating reports for cystic fibrosis carrier testing through a rapid user-centered design process that built on a previously developed generic template. We evaluated the new reports' communication efficacy and effects on comprehension against comparable reports used in current clinical practice. Methods: Thirty participants took part in three rounds of interviews. Usability problems were identified and rectified in each round. One hundred ninety-three participants took part in an evaluation of the resulting reports measuring subjective comprehension, risk probability comprehension, perceived communication efficacy, and other factors, as compared with standard reports. Results: Participants viewing the user-centered reports rated them as clearer, easier to understand, and more effective at communicating key information than standard reports. Both groups ended up with equivalent knowledge of risk probabilities, although we observed differences in how those probabilities were perceived. Conclusion: Our findings demonstrate that by starting with a patient-friendly generic report template and modifying it for specific scenarios with a rapid user-centered design process, reports can be produced that are more effective at communicating key information. The resulting reports are now being implemented into clinical care.