Despite the high prevalence of breast cancer in the elderly population, these individuals are underrepresented in clinical trials evaluating breast cancer. Extrapolation from a young trial group to the heterogeneous elderly population is not justified; the elderly more often present with well-differentiated tumours and positive hormone-receptor status. Moreover, increasing age is associated with changes in organ functioning which may interfere with treatment efficacy and toxicity. Finally, the impact of breast cancer on the expected longevity of such patients decreases with age. Therefore, the treatment of elderly breast cancer patients, as recommended by national guidelines, is not evidence-based. Because of the great heterogeneity, randomized trials are difficult to achieve in the elderly. We therefore stress the importance of alternative study designs to realise evidence-based medicine in this ever-growing population.