beta-Xylosidase gene (xylB) from Bacillus sp. was amplified and inserted between GAL10 promoter and GAL7 terminator. For the secretory production of xylB in Saccharomyces cerevisiae, in-frame fusion of the exoinulinase signal sequence (INU1s) of Kluyveromyces marxianus to the upstream of xylB was conducted. When a transformant of S. cerevisiae harboring the resulting plasmid was grown on galactose-containing medium, most of beta-xylosidase activity was localized in the periplasmic space of yeast and a maximum total activity reached about 2.9 unit ml(-1) at 42 h cultivation. The recombinant beta-xylosidase was produced as an active dimer form.