One of the most fundamental challenges to multicellular life is the delivery of sufficient oxygen and metabolic substrate to all cells and the rapid elimination of acidformed during cellular respiration. Thus it is logical to wonder whether anemia, by compromising these pathways, might contribute to the progression of cancer. Anemia has been identified as a predictive factor for decreased survival in settings other than oncology, though a cause/effect relationship has not yet been proved. Most clinicians accept the premise that anemia compromises radiotherapy and that hypoxic tumor cells exhibit resistance to chemotherapy, and there is now abundant evidence that the quality of life and functional status of cancer patients is significantly compromised as hemoglobin levels fall below 12 g/dL. The availability of safe and effective therapies for the anemia of cancer, coupled with recent evidence that anemia itself may well have an impact on survival, make it important that the potential of anemia therapy to improve survival outcomes in cancer patients be explored in clinical trials. This article reviews the data available regarding the impact of anemia on the survival of cancer patients.