In the past ten years high-dose chemotherapy with autologous haematopoietic stem-cell support (HD-CT) has increasingly been used for breast cancer. But the vast majority of trials are small phase I/II studies showing until now not enough evidence that HD-CT is superior to conventional-dose chemotherapy (CD-CT). In contrast to this, the public perception of this treatment is different. Patients as well as physicians often uncritically believe in reports contrasting the positive results obtained in case series treated by HD-CT with those of historical control groups. This leads to the problem that many patients and also clinicians are not willing to participate in randomized trials on this topic. A critical assessment of current knowledge on the effectiveness of HD-CT in breast cancer is given. The problems related to the use of historical controls, in general, and especially in the setting of HD-CT are demonstrated. Using data of patients treated with CD-CT within trials of the German Breast Cancer Study Group (GBSG) it will be shown that results similarly favorable to those reported from patients treated with a high-dose regimen may be produced using quite simple selection mechanisms. Comparisons of patients treated with HD-CT with historical control groups of patients treated with CD-CT may be misleading. A valid treatment comparison is only possible by means of large randomized trials. Clinicians should participate in the ongoing trials and enter all eligible patients.