A cytogenetic and clinical study of an intersexual Arabian horse revealed it to be a genetic female but a gonadal male intersex. This corresponds in general to previously reported cases, which have been genetic females despite the presence of male gonads (or ovotestes). The reliability and ease of polymorph sexing in the horse as a method of determining the genetic sex has been confirmed. Once this is known an easy decision can be made as to the feasibility of castration or not. In the case described castration resulted in an improved feminine appearance.