Mos 45,X/46,X,Y with no bright fluorescence was studied in 4 patients presenting variable phenotypes, from Turner's syndrome, with or without virilization, to ambiguous external genitalia, with combined cytogenetic techniques. G-11 staining demonstrated, in all cases, that the abnormal Y was a dic(Yp). Considerations about the possibility that some of the 46,X,Yq-males attending infertility clinics may be examples of dic(Yp) are made.