6 patients with anaemia associated with myeloma multiplex were treated with human recombinant erythropoietin (rHuEPO, Exprex*) at a dose of 150 units/kg s.c. three times a week for 12 weeks. A good response, defined as an increase of hemoglobin > 20 milligrams above the pretreatment level, was achieved in 4 patients. The erythropoietin serum concentration was measured four times in each patient: twice before commencing and twice after completing the treatment. In patients who responded to rHuEPO therapy the Epo serum concentration decreased whereas in non-responders increased.