Introduction: The American Academy of Pediatrics (AAP) recommends exclusive breastfeeding prior to 6 months of age. However, many women are unable to produce enough milk to exclusively breastfeed their child and, thus, supplement infant diets with formula or donor breast milk (DBM). Though DBM is the ideal supplement to comply with AAP guidelines, it is often difficult for parents to obtain DBM safely from milk banks (MBs) and they are increasingly turning to informal “mother-to-mother” milk sharing (IMS) instead. Though this practice is discouraged by the AAP as it is potentially unsafe, few studies have examined parental perceptions of DBM and its sources. Purpose: To study motivations and concerns regarding DBM usage from MB and IMS. Methods: An anonymous survey was posted on Facebook and shared 330 times by various pages, including La Leche League USA, local La Leche Leagues, and state and local breastfeeding coalitions. Participants who self-identified as recipients of DBM reported from where they received DBM, why they chose that DBM source, and what concerns they had regarding DBM use as well as demographic questions. Results: A total of 655 responses (MB recipients: 35.6%, n=233; IMS 64.4%, n=422) were analyzed; 90.5% white. Of those who chose IMS, 55.9% (n=236) did not have any DBM concerns and 78.2% (n=330) stated that they did not medically screen the donors because they “trusted them.” The greatest concerns over using DBM from IMS were alcohol/drug transmission (27.5%, n=116), potential disease transmission (24.6%, n=107), and bacterial contamination (19.7%, n=83) (Table 1). Motivations for using IMS over MBs were MB costs (53.3%, n=225), concerns about pasteurization affecting DBM quality in MBs (26.5%, n=112), and the inability to obtain prescriptions for MB DBM (23.0%, n=97). MB recipients cited health professional recommendation (45.5% n=106) and safety of breast milk (38.6%, n=90) as motivations for using MB (Table 2). Conclusion: Most respondents who reported obtaining DBM did so informally and the majority indicated they did not have concerns or take measures to reduce risks associated with IMS. It is clear that IMS participants underestimate these risks and, consequently, it is imperative that physicians educate parents on MBs and encourage safe milk sharing practices, including screening all potential donors in order to mitigate risks of disease and drug transmission through DBM.