pcDNA3.1/myc-His(-) A, B, and C are 5.5 kb vectors designed for overproduction of recombinant proteins in mammalian cell lines. The vectors are supplied in three reading frames to facilitate in frame cloning, with a C-terminal peptide containing a polyhistidine metal-binding tag and the myc (c-myc) epitope. The human cytomegalovirus immediate-early (CMV) promoter provides highlevel expression in a wide range of mammalian cells. In addition, the vector will replicate episomally in cell lines that are latently infected with SV40 or that express the SV40 large T antigen (e.g. COS7). High-level stable and nonreplicative transient expression can be carried out in most mammalian cells. The control plasmid, pcDNA3.1/myc-His(-)/lacZ, is the pcDNA3.1/myc-His(-) A vector with a 3.2 kb fragment containing the β-galactosidase gene cloned in frame with the C-terminal peptide. It is included for use as a positive control for transfection, expression, and detection in the cell line of choice.