Single GATA-6 (G6gcko), GATA-4 (G4gcko), and double GATA-4/6 (G4/6gcko) granulosa cell-specific knockout mice were generated to further investigate the role of GATA transcription factors in ovarian function in vivo. No reproductive defects were found in G6gcko animals. G4gcko animals were subfertile as indicated by the reduced number of pups per litter and the release of significantly fewer oocytes at ovulation. In marked contrast, G4/6gcko females fail to ovulate and are infertile. Furthermore, G4/6gcko females had irregular estrous cycles, which correlate with the abnormal ovarian histology found in unstimulated adult G4/6gcko females showing lack of follicular development and increased follicular atresia. Moreover, treatment with exogenous gonadotropins did not rescue folliculogenesis or ovulation in double-knockout G4/6gcko mice. In addition, ovary weight and estradiol levels were significantly reduced in G4gcko and G4/6gcko animals when compared with control and G6gcko mice. Aromatase, P450scc, and LH receptor expression was significantly lower in G4gcko and G4/6gcko mice when compared with control animals. Most prominently, FSH receptor (FSHR) protein was undetectable in granulosa cells of G4gcko and G4/6gcko. Accordingly, gel shift and reporter assays revealed that GATA-4 binds and stimulates the activity of the FSHR promoter. These results demonstrate that GATA-4 and GATA-6 are needed for normal ovarian function. Our data are consistent with a role for GATA-4 in the regulation of the FSHR gene and provide a possible molecular mechanism to explain the fertility defects observed in animals with deficient GATA expression in the ovary.