SummaryInEscherichia coli, the binding protein‐dependent transport system for maltose and maltodextrins is composed of five proteins — LamB, MaIE, MaIF, MaIG and MaIK — located in the three layers of the bacterial envelope. Proteins MaIF and MaIG are hydrophobic inner membrane components mediating the energy‐dependent translocation of substrates into the cytoplasm. In this paper, we analyse the topology of the MaIG protein by using methods based on the properties of fusions betweenmaIGand‘phoA, a truncated gene encoding alkaline phosphatase lacking its translation initiation and exportation signals. Fusions were obtained by using either phage λTnphoAor by constructingin vitrofusions located randomly within themaIGgene. The deduced topological model suggests that MaIG spans the membrane six times and has its amino‐ and carboxy‐termini in the cytoplasm. These results will be helpful for the interpretation of the phenotypes of