We have isolated the human homologue of the murine erythropoietin receptor (mEPO-R) from an erythroleukemia line, OCIM1, and from fetal liver. Both the cDNA and protein sequence of the human receptor were 82% homologous to the mEPO-R. Heterologous expression of the human cDNA in COS cells yielded a protein of about 66 Kd. The protein could be specifically immunoprecipitated with either an antibody raised against the amino terminus of mEPO-R or by a monoclonal antibody that bound EPO bound to its receptor. Cross-linking of radioiodinated EPO to COS cells expressing the human EPO-R gave apparent molecular weights of 66 and 100 Kd for the receptor. The murine interleukin-3-dependent pre-B- lymphocyte cell line, Ba/F3, was made EPO-dependent by transfection of the human cDNA into the cells and selecting for growth in EPO- containing media.