In 1985, we were in charge of the femininity control tests for the participants of the XXth Universiade in Kobe. At that time, we chose as screening tests checking both X chromatin from buccal mucous membrane and Y chromatin from hair roots. The number of female competitors who attended the Universiade, except tennis, gymnastics, and fencing, was 631. Among them, 108 had already had the certificate of femininity so we examined 523 female competitors. All but three of them were normal for femininity, i.e., X chromatin positive and Y chromatin negative. Two of the three exceptions were Y chromatin positive and X chromatin negative. Chromosomal analyses from their peripheral lymphocytes showed a pattern concordant with a 46,XY karyotype. The other was both X and Y chromatin positive, but we could find Y chromatin on only one slide out of three. Since this person refused to have a blood sample taken, we can only suppose her karyotype as being 46,XX/46,XY or 46,XX/47,XXY. This last case would not have been found, if we had checked only the X chromatin. From our experience, we conclude that for femininity control, it is safer to screen the Y chromatin. We would strongly advise the use of both X and Y chromatin tests for femininity control.