The proximal SF-1 binding site in intron 1 was replaced with one in which the genetic sequence was altered from TAGCCTTGA to TAGaaTTGA. A floxed neo cassette with a 3' lox P site was inserted in intron 1 but was removed by germ-line, cre-mediated recombination. Expression of the protein product was reduced 7-fold in the adrenal and testis but was unaffected in the placenta and ovary.