Bohlius et al identified risk factors for thrombo-embolic events in patients treated with recombinant human erythropoietin. A patient with one or more risk factors may benefit from closer monitoring or discontinuation of erythropoietin therapy. The authors are from the University of Cologne, University of Birmingham (UK), University of Frieburg, H. Lee Moffitt Cancer Center, Northwestern University, Veterans Administration Chicago and Chicago Blue Cross and Blue Shield.