Granulosa cells express the closely related orphan nuclear receptors steroidogenic factor-1 (SF-1) and liver receptor homolog-1 (LRH-1). To determine whether 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 FSH and testosterone, each significantly augmented progesterone production and mRNAs for cholesterol side-chain cleavage enzyme and 3β-hydroxysteroid dehydrogenase above that observed with FSH alone, with SF-1 being more effective than LRH-1. LRH-1 did not augment FSH-stimulated estrogen production, whereas SF-1 produced only a slight (∼30%) augmentation of FSH-stimulated estrogen production. The stimulatory actions of both were reduced by overexpression of 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 in the absence of FSH stimulated progesterone production and mRNAs for 3β-hydroxysteroid dehydrogenase and cholesterol side-chain cleavage enzyme but did not stimulate estrogen production or mRNA for aromatase. 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.