Steroid hormones regulate diverse biological functions, including programmed cell death (apoptosis). Although steroid receptors have been studied extensively, relatively little is known regarding the cellular targets through which apoptosis is triggered. We show here that the ligand-activated estrogen receptor (ER) induces apoptosis in an erythroid cell line by binding to, and consequently inhibiting the activity of, GATA-1, an erythroid transcription factor essential for the survival and maturation of erythroid precursor cells. GATA-1 inhibition is reflected in the downregulation of presumptive GATA-1 target genes. Constitutive overexpression of a GATA-binding protein resistant to the effects of the ER partially rescues ER-induced apoptosis. Induction of apoptosis by a mutant ER defective in binding to the estrogen response element but active in GATA-1 inhibition suggests that ER-mediated inhibition of GATA-1 is direct and does not require estrogen response element-dependent transcriptional activation. Thus, a lineage-restricted transcription factor, such as GATA-1, constitutes one cellular target through which steroid hormones may control apoptosis. As GATA-binding proteins are evolutionarily conserved, we speculate that members of the steroid receptor family may exert some of their diverse biological functions in different cellular contexts through interference with the function of GATA-binding proteins.