In many dioecious plants, gender influences economic value, breeding schemes, and/or opportunities for commercial use of genetically transformed materials, The objective of this study was to identify molecular markers linked to sex determination loci in the dioecious plant Salix viminalis L, A 4 x 4 factorial mating design was used to identify sex ratios in full-sibling progeny, to generate a working genetics model for segregating sex ratios, and to search for molecular markers linked to sex determination genes, Bulked segregant analysis, utilizing 380 arbitrary decamer primers to generate randomly amplified polymorphic DNA (RAPD) products was initially applied to progeny sets from 3 of the 16 full-sibling families, Of the 1080 RAPD bands examined, only a single 560 bp band was shown to be linked to a sex determination locus, The same 560 bp band occurred in three additional full-sibling families and was present In one female parent and one male parent involved in the factorial mating design, This marker, UBC354(560), is biparentally inherited, is associated with femaleness in certain genetic backgrounds, and is linked to allele Al in the proposed two-locus epistatic genetic model of sex determination for S. viminalis. Southern blots confirmed marker homology among progeny and parents used in this study.