Plasmids were constructed carrying the loxP and FRT recognition sites for the Cre and Flp site-specific recombinases, respectively, within multiple cloning sites. Vectors carrying single and tandemly repeated targets are available with various flanking restriction enzyme sites. In addition, a series of plasmids carrying both loxP and FRT sites is available. These vectors facilitate construction of target molecules for these site-specific recombinases which are becoming increasingly important tools for the in vivo manipulation of DNA.