Although prophylactic mastectomy significantly reduces the incidence and recurrence of breast cancer, little is known about women's information needs before the procedure. We surveyed 967 women, from 6 healthcare systems, with bilateral or contralateral prophylactic mastectomy performed between 1979 and 1999. There were 2 open-ended questions: "What one thing do you wish you had known before your prophylactic mastectomy" and "Is there anything else you would like to share with us?" Three researchers categorized responses, and informational needs were ascertained. Seventy-one percent (684 women) responded, of which 81% answered one or both open-ended questions. There were 386 comments (made by 293 women) that related to information needs; 79% of women had bilateral prophylactic mastectomy and 58% had contralateral prophylactic mastectomy. Most concerns (69%) were related to reconstruction: the longevity; look and feel of implants, pain, numbness, scarring, and reconstruction options. Many women wished they had seen photographs to better prepare them for the final result. Our findings suggest that information needs of many women undergoing prophylactic mastectomy, particularly those selecting bilateral prophylactic mastectomy, have not been sufficiently addressed. Clinicians and health educators should be aware of patient needs and must counsel women accordingly.