[Twins in cattle. Freemartin or not a freemartin? Preliminary Communication].

The preliminary results of comparative studies designed to make it possible to establish a diagnosis of 'freemartin' are reported. Three methods were used, namely typing of the blood, chromosome analysis and determination of the length of the vagina. In a very large number of cases, the diagnosis may even be established in very young calves by measuring the length of the vagina. Laboratory studies may provide a solution in doubtful cases.