Three new S. pombe plasmids are described. Plasmids pSP3 and pSP4 are two Schizosaccharomyces pombe ars1 multicopy vectors with the Saccharomyces cerevisiae HIS3 or LYS2 genes as selectable markers. They complement the S. pombe his5-303 or lys1-131 mutations, respectively. Plasmid pSPars1 is a vector carrying the S. pombe ars1 and a unique NdeI site which allows the introduction of any selectable marker therefore bringing a unified vector backbone for the construction of new S. pombe/S. cerevisiae/E. coli shuttle vectors. These plasmids permit classical molecular genetic techniques to be performed directly.