Women from families in which many individuals have developed breast and/or ovarian cancer may request for DNA-testing. A DNA-test result may disclose their own risks to develop cancer (again),... Show moreWomen from families in which many individuals have developed breast and/or ovarian cancer may request for DNA-testing. A DNA-test result may disclose their own risks to develop cancer (again), their relatives__ risks and subsequent options for medical surveillance. This thesis describes several multicenter studies in the Netherlands about the psychological and medical impact of DNA-testing on the lives of these women and their relatives. Despite their accurate understanding of the global meaning of DNA-test result, many participants interpreted the result differently from what the genetic-counselor had actually communicated. Like in a children__s whisper game, their relatives also misinterpreted the information communicated by the first messenger. The messengers__ misinterpretation was not only related to their inaccurate thoughts about heredity and cancer in general, but also to their feelings, and especially to their unfulfilled need for certainty, sense of self and unresolved existential issues. The presence of misinterpretations predicted the extent of the counselees' distress and the medical decisions after DNA-test result disclosure. The study results are described in their historical and theoretical context, followed by practical clinical suggestions for genetic-counselors and psychologists. For instance, we suggest that genetic-counselor try to avoid the communication of ambiguous DNA-test results that do not have medical consequences. Show less