Absolute numbers (and box plots) of EPCs per high-power field before and after 8 weeks of rhEPO treatment in 11 patients with renal anemia. For comparison, we show absolute EPC numbers of 11 age- and sex-matched healthy subjects. The absolute number of functionally active EPCs in renal patients before rhEPO therapy was significantly lower than in healthy subjects (P < .01), but increased to comparable levels during treatment with rhEPO.