Recombinant erythropoietin was given to six renal anaemia patients (2 male and 4 female, aged 38-66 years) with chronic renal failure in the predialysis state. Eprex (Cilag, Switzerland) was used in the treatment. The preparation was administered subcutaneously, thrice weekly for 6 months, at a mean dose of 50 U/kg. The aim of the therapy was to keep haemoglobin in the target range of 100 and 120 milligrams. No allergic reactions or other forms of intolerance to the preparation were noticed. The mean baseline haemoglobin level prior to treatment (75.5 +/- 4.06 milligrams) increased to 96.3 +/- 6.9 milligrams at three months and 106.0 +/- 7.1 milligrams at six months (P < 0.01). The baseline MCHC increased from 313.6 +/- 2.7 milligrams to 324.3 +/- 4.29 milligrams (P < 0.05) during the third month of treatment. Hematocrit also increased significantly-from 0.23 +/- 0.01 to 0.31 +/- 0.01 (P < 0.01) during the third and to 0.36 +/- 0.02 (P < 0.001) during the sixth month of treatment. The erythrocyte counts from 2.73 +/- 0.2 x 10(12)/l reached 3.69 +/- 0.24 x 10(12)/l (P < 0.01) at three months and 4.01 +/- 0.27 x 10(12)/l (P < 0.001) at six months. Reticulocyte counts increased from 1.93 +/- 0.37/1000 to 4.06 +/- 0.6/1000 after one month of treatment (P < 0.02) reaching the highest values during the second week of treatment. After the fourth week, reticulocyte number fluctuated slightly but not significantly above the baseline. The serum iron decreased from 12.0 +/- 0.36 mumol/l to 10.5 +/- 1.0 mumol/l (P < 0.05) and 9.93 +/- 0.9 mumol/l (P < 0.02) at three and six months, respectively. The results revealed a non-significant reduction of serum ferritin and transferrin in the course of treatment. We also found a strong positive correlation between the dose of Eprex applied and the haemoglobin, hematocrit and the erythrocyte values in the treated patients.