A missense G > A SNP (Arg > Gln) in exon 7 of the CYP11B1 gene, involved in the biosynthesis of adrenal corticoids, has been found to contribute to congenital adrenal hyperplasia and associated gynecomastia, empty scrotum, and aggressive behavior in a tomcat with a normal 38,XY chromosome set14. Here, CYP11B1 is linked to congenital adrenal hyperplasia.