Objectives: Expanding the existing Breast Cancer Family Registry (BCFR) to enrol daughters aged 6-17 years in a prospective cohort study named LEGACY (Lessons in Epidemiology and Genetics of Adult Cancer from Youth) offers the opportunity to study the effects of genetic and environmental exposures in youth on adult breast cancer risk. Few studies have assessed parents' willingness to enrol their daughters in genetic epidemiological cohort studies. Since BCFR parents are the gatekeepers of their daughters' future enrolment, it is important to explore their interests and attitudes towards LEGACY.Methods: Semi-structured telephone interviews were conducted with 85 BCFR participant parents at 3 BCFR sites in Ontario, Canada, and in Utah and Northern California. We explored parents' thoughts and feelings (interests and attitudes) regarding their daughters' enrolment in LEGACY and different data collection modalities. Qualitative analysis of audiotaped interviews was carried out utilizing an inductive content analysis.Results: Parents' acceptance of three data collection modalities were 92% (78/85) for questionnaire data, 87% (74/85) for biological samples and 63% (46/73) for physical examination for pubertal staging. The parents' primary motivation for participation was altruistic. Their concerns regarding their daughters' participation centered on exacerbating awkward pubertal feelings, increasing cancer anxiety, respecting autonomy and maturity, privacy and future use of data and logistical impediments.Conclusion: Parents demonstrated a high level of interest in the creation of LEGACY. Their motivation to participate was balanced by their desire to protect daughters from undue harm. These interviews contributed valuable information for the design of LEGACY. Copyright (c) 2009 John Wiley & Sons, Ltd.