It is an honour and pleasure to be Guest Editor for this special issue oΐActa Haematologica based on oral presentations given at a satellite symposium 'Current and Potential Applications for Erythropoietin' at the 11th meeting of the International Society of Haematology in Basel, Switzerland, 1st September 1991. It is intended that the supplement will bring the reader up to date with new information relating to some of the current and potential applications for recombinant human erythropoietin

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... r-HuEPO) in correcting anaemia of different forms. Pedrazzini has concisely summarized what is known to date. It is clear that when there is a lack of endogenous erythropoietin (EPO), such as in chronic renal failure (CRF), replacement therapy is dramatically effective. However, beyond the simple lack of endogenous EPO in CRF, it has proved more difficult to identify other patient populations for r-HuEPO therapy and to select the optimal dose and regimen for treatment. With this in mind, it is helpful to categorize patients in terms of the magnitude and type of erythropoietic deficiency (table 1) . All these factors need to be considered both in designing trials and in assessing the outcome. Each chapter in this issue addresses the problems of patient selection, dose and scheduling of r-HuEPO regimens. The study of Abels et al. is particularly encouraging: subsets of patients with a broad range of cancers benefit from r-HuEPO therapy. As also illustrated by the early data by James et al., there appears to be a particular benefit with r-HuEPO for platinum-containing regimens. The somewhat conflicting data in patients with myelodysplastic syndromes reflect the heterogeneity in these diseases. Clearly, a subset of patients can benefit from r-HuEPO, although early changes in serum transferrin concentrations do not predict response. As for other disease categories, the early identification of responding patients is important to avoid trials of potentially very expensive, but ineffective therapy. The possible benefit of short-term r-HuEPO in anaemic premature infants is interesting and the follow-up data in this regard will be of importance. In planning new strategies for use of r-HuEPO it is helpful to remember the three categories of therapy listed in table 2. Obviously different doses and scheduling are necessary in each category. The study of Hörl et al., evaluating optimal dose and r-HuEPO regimen in CRF patients, is of major practical importance. The fact that the 3-times weekly subcutaneous regimen is the most cost-effective is a very valuable piece of information both for individual patients or physicians as well as for the health care authorities. In future, it will be increasingly important to identify subgroups of patients with the highest likelihood of response as well as to develop and select the optimal dose and regimen to minimize