Anti-Müllerian hormone (AMH) is a member of the transforming growth factor beta superfamily, which plays a major role during reproductive development in eutherians. We isolated and characterized in rainbow trout an amh genomic sequence. In trout, this gene spans a region of 2,700 bp and is encoded by 6 exons (and 5 introns). The promoter sequence contains one highly conserved SF1 binding site, but no consensus SOX binding site, despite the essential role of Sox9 in the regulation of AMH in mammals. Using in situ hybridization, amh expression was detected both in male and female gonads during sex differentiation, and localized to the somatic cells surrounding germ cells with a stronger expression in the differentiating testis than in the ovary.