The primary aim of the present study was to examine the relationship of changes in hemoglobin levels following recombinant human erythropoietin (rHuEPO) treatment to changes in cognitive functioning studied by Mini Mental State Examination (MMSE) in elderly cancer patients undergoing chemotherapy treatment. The secondary aim was that to assess the relationship of changes in hemoglobin levels following rHuEPO treatment to changes in functions studied by Comprehensive Geriatic Assessment (CGA), such as Activity of Daily Living (ADL), Instrumental Activities of Daily Living (IADL), Geriatric Depression Scale (GDS) and the Mini Nutritional Assessment (MNA). To this end, hemoglobin levels and cognitive functioning were evaluated in a sample of cancer patients prior to the start of chemotherapy treatment and again after 4, 8 and 12 weeks of treatment with chemotherapy plus rHuEPO. Ten elderly patients (mean age 71.4 years) were enrolled. At baseline, enrolled patients had a mean Hb value of 10.3g/dl. After 4 weeks of rHuEPO treatment, Hb values increased significantly (p<0.0001), with a mean increase of 1.2g/dl (range: 0.2-2.1). Remarkably, 8 out of 10 (80%) showed an increase of Hb levels >or=1g/dl in comparison to baseline and therefore were considered responders. At baseline, four patients (40%) showed a moderate cognitive impairment, whilst six patients (60%) showed a normal cognitive function. After 4 weeks of rHuEPO treatment nine patients (90%) showed a significant improvement of cognitive functions in comparison to baseline (p<0.005): eight of them were responders also to rHuEPO in terms of correction of anemia. The Spearman's rank correlation test showed a statistical significant correlation between Hb increase and increase in cognitive functioning assessed by MMSE after 4 weeks (p=0.049), 8 weeks (p=0.044) and 12 weeks (p=0.031) of rHuEPO treatment. Therefore, the findings of this study provide support for the hypothesis that significant increases in hemoglobin over the course of chemotherapy supplemented with rHuEPO administration would be accompanied by significant improvement in cognitive performance over the same interval.