The results of the multicenter trials demonstrate that r-HuEPO therapy can increase the hematocrits of anemic patients with advanced cancer. The multicenter trials were undertaken because, in previous smaller trials without placebo controls, patients with cancer and anemia had been shown to be likely responders to r-HuEPO therapy. To varying degrees in these trials, RBC transfusion requirements were eliminated or decreased in comparison to those of placebo-treated patients, and anemia was lessened or corrected in the r-HuEPO groups. The side effects of r-HuEPO treatment were minor; anemic patients with advanced cancer receiving r-HuEPO therapy did not develop significant hypertension, seizures, or thrombotic events, and progression of tumor was not observed. Moreover, patients in the multicenter trials whose hematocrits increased to 38% or greater, or increased 6 percentage points or more, experienced significant improvement in all aspects of the quality of their lives. On the basis of these trials, r-HuEPO therapy appears to treat effectively the anemia of cancer. The importance of eliminating the need for transfusions and preventing sensitization to human leukocyte antigens will be major factors affecting the clinical future of r-HuEPO.