Since the cloning of BRCA1 and BRCA2, genetic testing for breast and ovarian cancer susceptibility has become more widespread. However, interpretation of test results is not always straightforward. To illustrate this point, five vignettes adapted from actual cases are presented. As these cases demonstrate, in many high-risk families, a deleterious mutation in BRCA1 or BRCA2 is not identified in an affected proband. There are several potential explanations for such a finding, namely that an undetected mutation in BRCA1 or BRCA2 may exist, or there could be a mutation in a rare or undiscovered gene. In addition, the possibility that women with breast cancer represent sporadic cases within hereditary cancer families must also be considered. Finally, the occurrence of BRCA1/2 variants of uncertain significance, often missense mutations, further complicates the risk assessment. In some of these instances, extending testing to relatives can be helpful to clarify results. When hereditary breast cancer cannot be ruled out, individuals may still be at increased risk for cancer and therefore need to obtain appropriate surveillance. The process of genetic counseling is critical both before and after testing to ensure that patients understand the potential medical and psychosocial implications of testing and are aware of available options and resources. A multidisciplinary approach to service delivery, which includes clinicians in genetics and oncology, can facilitate patients' decision making and provide continued access to information and support.