Objective. Studies examining the relationship between adverse life events and breast cancer have produced conflicting results. A systematic review of the published studies was therefore carried out. Methods. Electronic databases and bibliographies of review articles were searched for studies in any language. Studies were assessed for methodological quality by two reviewers. Results. Twenty-nine studies were found. These were of variable quality. Random effects meta-analysis of the higher quality studies found no significant relationship between breast cancer and either bereavement (summary odds ratio(OR)=0. 9;95% confidence interval (CI) 0. 57 to 1. 45) or other adverse life-events (summary OR=0. 8; 95% CI 0. 61 to 1. 06). Funnel plots may be suggestive of publication bias, with small studies reporting negative findings less likely to be published. Conclusions. Good quality case-control studies, and the single large prospective study in this area, do not support the hypothesis of a casual relationship between adverse life events and onset of breast cancer.