To address whether the use of bisphosphonates in the adjuvant setting of breast cancer might have any effect on the natural course of the disease, a meta-analysis was conducted of published and unpublished randomized controlled trials found in PubMed, the Cochrane Central Register of Controlled Trials, the ISI Web of Knowledge, and abstracts of major international conferences up to January 2009. All trials that randomized patients with primary breast cancer to undergo adjuvant treatment with any bisphosphonate versus non-use were considered eligible. Analysis included data from 13 eligible trials involving 6886 patients randomized to treatment with bisphosphonates (n = 3414) or either placebo or no treatment (n = 3472). Compared with no use, adjuvant breast cancer treatment with bisphosphonates did not reduce the overall number of deaths (odds ratio [OR], 0.708; 95% CI, 0.482-1.041; P = .079), bone metastases (OR, 0.925; 95% CI, 0.768-1.114; P = .413), overall disease recurrences (OR, 0.843; 95% CI, 0.602-1.181; P = .321), distant relapse (OR, 0.896; 95% CI, 0.674-1.192; P = .453), visceral recurrences (OR, 1.051; 95% CI, 0.686-1.609; P = .820), or local relapses (OR, 1.056; 95% CI, 0.750-1.487; P = .756). No significant heterogeneity was observed among the trials except for estimates of deaths and disease recurrences (P = .034 and P = .016, respectively). In subgroup analyses, use of zoledronic acid was associated with a statistically significant lower risk for disease recurrence (OR, 0.675; 95% CI, 0.479-0.952; P = .025). However, these results should be interpreted with caution because the statistical significance for this association was weak and might be attributed to chance from multi-test analyses. Use of zoledronic acid was not associated with any significant difference in death (OR, 0.642; 95% CI, 0.388-1.063) and bone metastasis rates (OR, 0.661; 95% CI, 0.379-1.151). Currently available evidence does not support the hypothesis that use of bisphosphonates in adjuvant treatment of early breast cancer will alter the natural course of the disease. Nonetheless, a nonsignificant trend seems to exist for better outcomes in patients undergoing bisphosphonate treatment. Until further evidence from new clinical trials becomes available, adjuvant bisphosphonates should not be recommended routinely.