The mitotic chromosomes in primary cultured cells from mouse embryos of the translocation stocks, T(5;18)26H, T(5;11)7Ca, and T(14;17)264Ca, have been identified by their distinctive fluorescent-banding patterns after staining with quinacrine mustard. In this way, linkage group (LG) V has been assigned to chromosome 2, LGXVIII to chromosome 9, and LGXIV and LGXVII to either of chromosomes 3 or 13. The assignment of LGXI to chromosome 6 has been confirmed. The centromeres of chromosomes 1 (LGXIII), 2 (LGV), 9 (LGXVIII), and 16 (LGIX) have been located at the ends nearest the genes fuzzy (fz), Danforth's short tail (Sd), nervous (nr), and T of their respective linkage groups by a cytogenetic method. The centromere of the X (LGXX) has been tentatively assigned to the end nearest to the scurfy (sf) locus.