We report that Gata-2 is expressed in a sexually dimorphic fashion during mouse gonadogenesis. Gata-2 transcripts accumulate rapidly in the fetal ovary from 11.5 days post coitum (dpc) onwards, but are not detected in the fetal testis throughout the period studied (10.5-15.5 dpc). Ovarian expression of Gata-2 ceases by 15.5 dpc. Examination of ovaries from embryos homozygous for the extreme allele of c-kit(W(e)) (Nature, 335, 88; Cell, 55, 185) demonstrates that ovarian Gata-2 expression is dependent upon the presence of germ cells. Comparative in situ hybridisation using the germ cell marker Oct4 (EMBO J., 8, 2543) indicates that Gata-2 transcripts are restricted to the germ cell lineage at 13.5 dpc.