A case of intersexuality in a Dorset horn ewe is described. Although possessing female external genitalia this animal had a male internal reproductive tract with inguinal testes, epididymes, vasa deferentia and seminal vesicles. No traces of cervix or uterus were present and the vagina was represented in its caudal part only. Chromosomal studies revealed chimaerism in peripheral leucocytes of the type 54, XX/54, XY, while other tissues revealed the normal female karyotype 54, XX. The ewe was born in a set of triplets with one dead male fetus and one living male. It was therefore concluded that the animal was a freemartin. The significance of this case and of the phenomenon of freemartisism in sheep is discussed.