Background: Short-term memory (STM) decline in breast cancer patients resulting from chemotherapy was evaluated by means of blood biomarkers, a questionnaire, and a computerized STM test. Methods: This study was conducted from January 2013 to June 2013, recruiting 90 subjects: 30 breast cancer patients beginning the 3rd of 4th cycles of docetaxel and cyclophosphamide chemotherapy, 30 recovered patients (who completed 4 cycles of docetaxel for a minimum of 6 months), and 30 healthy subjects (disease-free females). The levels of hemoglobin, red and white blood cells, and cortisol in serum, and a computerized STM test were analyzed to estimate the effects of chemotherapy on STM. A questionnaire was given to all subjects to assess quality of life. Results: Statistically significant differences were observed for the blood parameters (hemoglobin, red and white blood cells, and cortisol levels) between healthy and on-treatment subjects (respectively 13.47±0.96 g/dL vs 5.37±0.38 g/dL, 4.58±0.41 10¹²/L vs 2.07±0.13 10¹²/L, and 6.15±1.03 10⁹/L vs 0.86±0.41 10⁹/L). Scores of the STM test were significantly lower for patients compared to healthy subjects. As indicated by the results of the questionnaire, breast cancer patients had a higher tendency to forget than healthy controls (X²=3.15; p<0.0001) and recovered subjects (X²=3.15; p<0.0001). Conclusion: We found depleted levels of hemoglobin, red and white blood cells as a result of chemotherapy, and elevated levels of stress correlated with poor performances in the computerized STM test. A higher cortisol level might be an important precursor of STM deterioration. Monitoring cortisol would be beneficial for evaluating the quality of life of breast cancer patients on chemotherapy. Copyright © 2013 Wichtig Publishing - Milano (Italy).