Aim of this work was to investigate the roles of Wt1, Sox9 and Dmrt8 in murine gonad development. In the first part, gene expression in urogenital ridges of Wt1-/- and Wt1+/+ was compared, to identify new Wt1 target genes. Further analysis showed that AmhrII, one of the identified potential targets, is indeed regulated by Wt1. The second part describes the expression pattern of two newly identified murine Dmrt8 genes, Dmrt8.1 and Dmrt8.2, with potential roles in gonad development or gonadal function. In the third part a conditional Sox9 knock-out mouse, generated by collaboration partners, was used, to investigate the role of Sox9 during sex determination.