Before designing an intervention to assist women in making informed decisions about BRCA1 testing, we conducted focus groups with women who had breast cancer and unaffected women whose relatives had it to better understand women's knowledge, concerns about testing, and potential influences and support needs in making a decision about genetic testing for susceptibility to breast cancer. Findings show a general lack of knowledge about genetic testing for breast cancer and what it means to have a positive test result, a strong concern for family members, particularly daughters, to use information from testing to help them make better decisions about their health and lifestyle choices, a strong sense of altruism, particularly among affected women, about being tested to help other women, not just family, and various support needs surrounding the testing experience, including an active role for physicians in the decision process. The major advantages to testing seem to be for information that could help reduce uncertainty and assist with making future decisions about medical treatment and plans for surveillance and some lifestyle changes. The major disadvantages to testing were concerns about confidentiality and loss of insurance, the lack of proven options for women after testing, and stress from knowing one had the BRCA1 mutation. These focus group discussions show women's concerns and ambivalence about genetic testing. We need to provide women with balanced information about the positive and negative aspects of such testing, determine how best to involve physicians in women's decisions about testing, consider the effects of testing on family relationships, and provide more public education about what genetic testing is and what it means.