The diagnosis and subsequent treatment of cancer is for most people a major life stress.  At this time emotional distress such as anxiety, fears about cancer recurrence, concern about changes in body image, sexuality, and fears about the impact of the cancer on the family and significant others are common.  A source of support that has high uptake internationally both in breast cancer and across other cancer types is peer support, with recipients of such support reporting that interaction and discussion with people who have had a similar cancer experience provides a unique source of informational and emotional support, encourages hope for the future, normalises the experience, and reduces feelings of social isolation.  Peer support is distinct from professional support as it is founded on the principles of self-help, community and volunteerism.  Peer support provides an avenue for open emotional expression, storytelling, sharing of concerns, social identification and the creation of close connections between women who have experienced breast cancer.  However providing evidence of the benefits of peer support raises a number of challenges.  First, as a naturally occurring ecological phenomenon, standard randomised control trial methodologies cannot be easily applied to peer support.  Second, standard measures that are focussed on distress measurement as an outcome may not be sensitive to the benefits accrued from peer support.  This presentation will overview the evidence for peer support and suggest alternative approaches to evidence of benefit for this support method.