Transfer of mapping information between related species has facilitated the development of restriction fragment length polymorphism (RFLP) maps in the cereals. Sequence tagged site (STS) primer sets for use in the polymerase chain reaction may be developed from mapped RFLP clones. For this study, we mapped 97 STS primer sets to chromosomes in wheat and barley to determine the potential transferability of the primer sets and the degree of correspondence between RFLP and STS locations. STS products mapped to the same chromosome group in wheat and barley 75% of the time. RFLP location predicted STS location 69% of the time in wheat and 56% of the time in barley. Southern hybridizations showed that most primer sets amplified sequences homologous to the RFLP clone, although additional sequences were often amplified that did not hybridize to the RFLP clone. Nontarget sequences were often amplified when primer sets were transferred across species. In general, results suggest a good probability of success in transferring STSs between wheat and barley, and that RFLP location can be used to predict STS location. However, transferability of STSs cannot be assumed, suggesting a need for recombinational mapping of STS markers in each species as new primer sets are developed. Key words : sequence tagged sites, PCR, wheat, barley.