Abstract: The present invention provides a dual selection cassette (DSC) comprising first and second DNA segments having homology to a eukaryotic viral vector, positive and negative selection genes, each operably linked to their own promoter, and one or more unique restriction enzyme sites (URES) or site-directed homologous recombination sites. The present invention also provides a plasmid, pN/P, comprising an independent positive selection marker gene, an origin of replication, and a dual selection cassette. The dual selection cassette and pN/P plasmid can be used to produce eukaryotic gene transfer vectors without requiring temporally-linked double recombination events or the use of specialized bacterial strains that allow the replication of plasmids comprising defective origins of replication. This method usefully increases the ratio of desired to undesired plasmid and vector constructs. Additionally, this invention provides a method for the creation of eukaryotic viral vector libraries.