Cancer and treatment-related anaemia is a significant clinical problem. Erythropoiesis stimulating agents (ESA) improve anaemia and ultimately enhance patients' quality of life. However, about one-third of patients do not respond to ESA administration, mostly because of the impaired supply of iron to the erythroid marrow (functional iron deficiency). Concomitant administration of intravenous (IV) iron may improve responsiveness. The use of baseline predictors of response to ESA and of indicators of appropriateness of response and iron availability should allow targeted therapeutic interventions with both ESA and IV iron. Several biochemical and haematological indicators of response and of iron balance have been studied, but firm criteria for their use have not yet been rigorously established. The commonly used early predictive markers of response to ESA, such as baseline endogenous erythropoietin levels and an increase in haemoglobin, reticulocytes, and soluble transferrin receptor levels during ESA treatment, have not proved reliable due to their low sensitivity and specificity. Traditional markers of iron availability, such as serum ferritin and transferrin saturation display interpretation pitfalls. The need for predictors and indicators of responsiveness to ESA and IV iron is still current and clinically relevant.