In the present paper we report the first example of fertility in a female with isodicentric X-formation and karyotype 45,X/46,X,del(X)(pter----p21.3)/46,X,idic(X)(qter----p21.3::p21.3- ---qter). Her daughter was phenotypically almost normal and presented a 46,X,del(X)(pter----p21.3) karyotype in all examined cells.