A maltose-inducible expression vector in Bacillus subtilis has been developed and characterized. The vector permitted beta-galactosidase expression at a high level (maximum activity, 8.16 U/ml) when induced and its expression was markedly repressed by glucose. Using this vector, we successfully expressed the other two genes, bioA and vgb. This thus provided a potential expression system for cloned genes in B. subtilis.