The past clinical experience has indicated a hematopoietic response to oral and parenteral androgens. In past few years animal studies have demonstrated erythroid response to steroid metabolites. Clinical studies in 8 patients have demonstrated response to etiocholanolone when mixed with prednisone acetate. As with the use of testosterone, there has been no clinical prediction that etiocholanolone would provide a predictable hematopoietic response. With the use of in vitro culture technique, the circulating stem cell pool will be studied in the peripheral blood of normal subjects as well as patients with bone marrow failure. The erythroid colony growth pattern will be defined as a response to different dose schedules of androgen derivatives as well as a variety of 5 beta steroid metabolites. The response to etiocholanolone will be used as the comparative reference since clinical in vivo responses have been obtained with this metabolite. Concurrently normal human bone marrow erythroid colony assay will be done. Whole marrow suspension as well as gradient separation for a "mononuclear" or stem cell group will be done to assess colony response to androgens as well as the different steroid metabolites. It is hoped that this procedure may allow for some prediction as to cellular response to different steroids. Such data may allow for some prospective planning of therapy programs for patients with bone marrow failure.