In this report we present a case of the male-to-female sex reversal syndrome in a Dachshund bitch. The animal was subjected for examination due to the enlargement of clitoris and male-type behaviour. The cytogenetic analysis (Giemsa staining and FISH with sex chromosome specific probes) revealed a normal male chromosome complement (78,XY). The molecular analysis of the SRY and SOX9 genes with the use of SSCP technique did not reveal any polymorphism. Blood testosterone concentration was low (0.75 ng/ml), thus the androgen insensitivity syndrome could be excluded. We suggest that this case may represent a persistent Müllerian duct syndrome.