A diabody comprising a first polypeptide chain and a second polypeptide chain, wherein said first and second polypeptide chains form a covalently bonded complex, and wherein: (A) said first polypeptide chain comprises a VL Domain of a first immunoglobulin (VL1), a VH Domain of a second immunoglobulin (VH2), and a charged cysteine-containing Heterodimer-Promoting Domain comprising the amino acid sequence of SEQ ID NO:12 ; and (B) said second polypeptide chain comprises a VL Domain of the second immunoglobulin (VL2), a VH Domain of the first immunoglobulin (VH1), and a charged cysteine-containing Heterodimer-Promoting Domain comprising the amino acid sequence of SEQ ID NO: 13 ; wherein said charged cysteine-containing Heterodimer-Promoting Domain of said first polypeptide chain is separated from said VH2 by a polypeptide linker consisting of the amino acid sequence of SEQ ID NO: 2 , and said charged cysteine-containing Heterodimer-Promoting Domain of said second polypeptide chain is separated from said VH1 by a polypeptide linker consisting of the amino acid sequence of SEQ ID NO: 2 ; and wherein said charged cysteine-containing Heterodimer-Promoting Domain of said first polypeptide chain and said charged cysteine-containing Heterodimer-Promoting Domain of said second polypeptide chain are covalently bonded to one another via a disulfide bond between the amino acid sequence of SEQ ID NO: 12 and the amino acid sequence of SEQ ID NO: 13 . wherein said first and second polypeptide chains form a covalently bonded complex, and wherein: (A) said first polypeptide chain comprises a VL Domain of a first immunoglobulin (VL1), a VH Domain of a second immunoglobulin (VH2), and a charged cysteine-containing Heterodimer-Promoting Domain comprising the amino acid sequence of SEQ ID NO:12 ; and (B) said second polypeptide chain comprises a VL Domain of the second immunoglobulin (VL2), a VH Domain of the first immunoglobulin (VH1), and a charged cysteine-containing Heterodimer-Promoting Domain comprising the amino acid sequence of SEQ ID NO: 13 ; (A) said first polypeptide chain comprises a VL Domain of a first immunoglobulin (VL1), a VH Domain of a second immunoglobulin (VH2), and a charged cysteine-containing Heterodimer-Promoting Domain comprising the amino acid sequence of SEQ ID NO:12 ; and (B) said second polypeptide chain comprises a VL Domain of the second immunoglobulin (VL2), a VH Domain of the first immunoglobulin (VH1), and a charged cysteine-containing Heterodimer-Promoting Domain comprising the amino acid sequence of SEQ ID NO: 13 ; wherein said charged cysteine-containing Heterodimer-Promoting Domain of said first polypeptide chain is separated from said VH2 by a polypeptide linker consisting of the amino acid sequence of SEQ ID NO: 2 , and said charged cysteine-containing Heterodimer-Promoting Domain of said second polypeptide chain is separated from said VH1 by a polypeptide linker consisting of the amino acid sequence of SEQ ID NO: 2 ; and wherein said charged cysteine-containing Heterodimer-Promoting Domain of said first polypeptide chain and said charged cysteine-containing Heterodimer-Promoting Domain of said second polypeptide chain are covalently bonded to one another via a disulfide bond between the amino acid sequence of SEQ ID NO: 12 and the amino acid sequence of SEQ ID NO: 13 . <EOS>