Several new broad-host-range vectors for the construction of protein fusions to the Escherichia coli lacZ gene have been developed. In all of the constructs, a multiple cloning site (MCS) containing unique restriction sites is located upstream of lac operon segments whose lacZ genes lack translational start signals. Some of the vectors (pPZ10, pPZ20 and pPZ30) also contain transcriptional terminators upstream of the MCS. The new vectors allow the fusion of genes to lacZ in all translational reading frames. Due to a higher copy number they allow direct screening in E. coli for weakly expressed foreign promoters. Their usefulness for gene analysis in Pseudomonas aeruginosa was demonstrated by construction and expression of a regA'::'lacZ-encoded protein fusion.