Over the last 35 years, classical CMF (combination chemotherapy with cyclophosphamide, methotrexate and fluorouracil) has been a milestone in the adjuvant treatment of women with breast cancer. However, after an early burst of success lasted just over 10 years, classical CMF has been supplanted by 'third-generation' regimens containing taxanes and anthracyclines. Questions have been raised in the past years concerning the true effectiveness of adjuvant CMF for specific subgroups of patients and particularly, recent retrospective data support the fact that the CMF might have a role in the treatment of patients with triple-negative breast cancer. One possible justification for supporting this role of CMF may be sought in the mechanism of action of drugs used in the regimen, as triple-negative cells may be sensitive to alkylating agents that cause double-strand breaks in DNA. The lesson learned from the CMF could lead us to identify new combinations of drugs that could include the optimal chemotherapy backbone for triple-negative breast cancer such as platinum compounds or alkylating agents or Poly (ADP-ribose) polymerase inhibitors. In conclusion, although we have learned a lot from the use of CMF, many questions are still open and hopefully stimulate our thinking, as clinicians, leading us to find new and more effective ways to treat breast cancer.