Granulosa cells express the closely related orphan nuclear receptors steroidogenic factor-1 (SF-1) and liver receptor homolog-1 (LRH-1). To determine if SF-1 and LRH-1 have differential effects on steroid production, we compared the effects of overexpressing LRH-1 and SF-1 on estrogen and progesterone production by undifferentiated rat granulosa cells. Adenovirus mediated overexpression of LRH-1 or SF-1 had qualitatively similar effects. Neither LRH-1 nor SF-1 alone stimulated estrogen or progesterone production, but when combined with follicle stimulating hormone (FSH) and testosterone, each significantly augmented progesterone production and mRNAs for cholesterol side chain cleavage enzyme (P450scc) and 3-hydroxysteroid dehydrogenase (3-HSD) above that observed with FSH alone, with SF-1 being more effective than LRH-1. LRH-1 did not augment FSH-stimulated estrogen production while SF-1 produced only a slight (approx. 30%) augmentation of FSH-stimulated estrogen production. The stimulatory actions of both were reduced by overexpression of DAX-1 (dosage-sensitive sex reversal, adrenal hypoplasia congenita, critical region on the X chromosome, gene-1). Expression of either LRH-1 or SF-1 together with constitutively active protein kinase B (PKB) in the absence of FSH stimulated progesterone production and mRNAs for 3-HSD and P450scc but did not stimulate estrogen production or mRNA for aromatase (P450arom). These findings demonstrate that LRH-1 and SF-1 have qualitatively similar actions on FSH-stimulated estrogen and progesterone production which would suggest that these factors may have overlapping actions in the regulation of steroidogenesis that accompanies granulosa cell differentiation.