The aim of this study was to evaluate the effect of correction of chronic anaemia on the physical performance and the cardiovascular response to effort in children with end-stage renal disease (ESRD) maintained by haemodialysis. Seven patients (mean age 13.9 years) underwent triangular-type treadmill exercise testing before [haemoglobin (Hb) 6.3 +/- 0.9 g/dl] and after (Hb 11.2 +/- 1.2 g/dl) anaemia correction with recombinant human erythropoietin (rHuEPO). After treatment, the work-load reached, the peak oxygen uptake and average ventilatory anaerobic threshold (VAT) values were significantly increased (P less than 0.01, P less than 0.001, P less than 0.05 respectively). VAT values, expressed as a percentage of normal values, increased from 55.7 +/- 16.6% to 82.4 +/- 21%. This improvement correlated well with the increase in Hb (r = 0.79). Oxygen pulse also increased significantly, when tested after anaemia correction. In conclusion, these data demonstrate that when the anaemia of children with ESRD is corrected with rHuEPO, there is a clear improvement in aerobic work capacity and effort tolerance.