A cell culture was established from a biopsy of the portio uteri of a 29 yr old normal female who is a carrier of a familial chromosome aberration. Her cells in culture have 46 chromosomes with a translocation involving the long arm of a Y chromosome attached to the short arm of chromosome 15. This culture, with a chromosome complement of 46,XX,-15,+der(Y),t(Y;15)(15qter.fwdarw.15p1::Yq11.fwdarw.Yqter)pat, could be useful in determining the function of the end of the long arm of the Y chromosome. Both the proband''s mother and her son are carriers of the translocation, and a niece is a carrier and has trisomy 21. The translocation was identified by trypsin-Giemsa banding and the involvement of Yq was confirmed by Quinacrine-banding.