A stimulatory effect on bone marrow erythroid cells was observed in normal rats treated with dexamethasone. The erythropoietic effects of dexamethasone were completely abolished in rats with bilateral nephrectomy. In addition, simultaneous administration of corticosteroid with antibodies against erythropoietin in normal rats also resulted in a complete inhibition of the stimulatory action of dexamethasone on the bone marrow erythroid compartment. These results suggest that dexamethasone stimulates erythropoiesis indirectly, through a previous stimulation of kidney erythropoietin production.