An expression vector for systematic protein overproduction in Bacillus subtilis has been constructed. It derives from pDG148 and combines the main property of this vector, i.e. conditional expression of the gene in response to isopropylbeta-D-thiogalactopyranoside, with (i) rapid orientated cloning by a ligation independent procedure and (ii) a ribosome binding site of high translational efficiency. When used for overproduction of several proteins in B. subtilis, this vector gave good levels of protein synthesis.