This chapter provides methods and insights into the use of broad-host-range plasmid vectors useful for expression of genes in a variety of bacteria. The main focus is on IncQ, IncW, IncP, and pBBR1-based plasmids which have all been used for such applications. The specific design of each vector is adapted to its use, and here we describe, as an example, a protocol for construction (in Escherichia coli) of large insert DNA libraries in an IncP type vector and transfer of the library to the desired host. The genes of interest will in this case have to be expressed from their own promoters and the libraries will be screened by a method that best fits the functions of the gene or gene clusters searched for.